People have been fretting about the “population problem” for at least fifty years. But over those five decades, the perceived problem has practically reversed. From the sixties to the eighties, the problems on people’s minds were overpopulation and the “population explosion.” The proposed solutions were usually government programs ranging from mild nudges (like free condoms and sex education) to horrific coercion (like India’s involuntary sterilizations and China’s one-child policy and forced abortions).[1]

During this period, libertarians were predictably quick to oppose government action and defend individuals’ right to have as many children as they wished.[2] But they also developed a more intellectually creative response. Under the seminal influence of Julian Simon, libertarians embraced the view that high and growing population is good. The title of Simon’s most famous book became a leading libertarian slogan: People are the ultimate resource.[3]

Over the last two decades, the perceived population problem has radically changed. Fertility has sharply fallen all over the world. It fell in less-developed nations, deflating long-standing Malthusian fears. But it fell in developed nations as well. Except for the United States and Israel, every modern economy now has fertility below the replacement rate.[4] Without high levels of immigration, most will see their populations fall in coming decades.[5] In Germany, Japan, and Russia, with total fertility rates around 1.3, population decline has already arrived.

Libertarians could celebrate these changes as proof that the problem of overpopulation solves itself whether or not governments do anything about it. But if Julian Simon and the intellectual tradition he inspired were right, libertarians should be experiencing severe cognitive dissonance. People with zero appreciation of Simon now worry about low birth rates and falling populations. How can those of us who long maintained that “people are the ultimate resource” fail to see anything amiss?

The easiest out for libertarians is to toss Simon’s pro-population arguments down the memory hole. We could hail economic growth and modernization for slaying the genuine dragon of overpopulation, and move on. The main problem with this easy out is that Simon’s arguments were correct. Indeed, population has benefits that Julian Simon himself undersold. My goal in this essay is two-fold. First, it is to recap and refine the case for population. Second, it is to find libertarian solutions for the world’s genuinely disappointing demographic trends.

The Case for People

There came to me the memory of reading a eulogy delivered by a Jewish chaplain over the dead on the battlefield at Iwo Jima, saying something like, “How many who would have been a Mozart or a Michelangelo or an Einstein have we buried here?” And then I thought, Have I gone crazy? What business do I have trying to help arrange it that fewer human beings will be born, each one of whom might be a Mozart or a Michelangelo or an Einstein—or simply a joy to his or her family and community, and a person who will enjoy life?

—Julian Simon, The Ultimate Resource 2

The case against population is simple: Assume a fixed pie of wealth, and do the math. If every person gets an equal slice, more people imply smaller slices. The flaw in this argument is that people are producers as well as consumers. More sophisticated critics of population appeal to the diminishing marginal product of labor. As long as doubling the number of producers less than doubles total production, more people imply smaller slices.[6]

These anti-population arguments have strong intuitive appeal. But they face an awkward fact: During the last two centuries, both population and prosperity exploded. Maybe the world just enjoyed incredibly good luck, but it makes you wonder: Could rising population be a cause of rising prosperity?

Yes. Economists’ central discovery about economic growth is that new ideas are more important than labor or capital.[7] The main reason we’re richer than we used to be is that we know more than we used to know. We know how one man can grow food for hundreds. We know how to build flying machines. We know how to build iPhones. Best of all: Once one person discovers a new idea, billions can cheaply adopt it.

Once you recognize the power of ideas, the value of population comes into focus.[8] People—especially smart, creative people—are the source of new ideas. Imagine deleting half the names in your music collection—or half the visionaries in the computer industry. Think how much poorer the world would be. But population doesn’t merely increase the supply of new ideas. It increases the demand as well. Suppose an idea is worth $1 per person, but takes a decade to develop. On an island with a hundred inhabitants, the idea would remain undiscovered; inventors are better off picking coconuts. But in a world with seven billion customers, inventors scramble to bring the new idea to market.

Consider languages. There are far more books, movies, and television shows in English than in Romanian. Supply is one reason: Far more writers and directors speak English than Romanian. But demand is also crucial: English-speaking customers are far more numerous. Michael Kremer’s celebrated “Population Growth and Technological Change: 1,000,000 B.C. to 1990” generalizes this insight to all of human history.[9] Small, isolated populations in places like Tasmania stagnate or regress.[10] Large, connected populations in places like Eurasia progress—and the pace of progress quickens as their populations multiply.

Population also enriches us in a more immediate way. Despite constant complaints about cities’ crowds and congestion, city folk gladly pay higher urban rents. Even introverts and outright misanthropes shell out massive premiums to live near millions of strangers. What are they after? The obvious answer is choices—choices about where to work, what to buy, how to play, and who to meet. These choices, like ideas, come from people—suppliers who offer them, and demanders who sustain them. When population goes up, everyone gets extra choices.

The population-choice connection is most visible in a city. But physical proximity is not essential. Thanks to modern communications and transport, people in the middle of nowhere still belong to a global civilization. Whether we’re urban, suburban, or rural, we all enjoy a vast menu of occupations, lifestyles, hobbies, cultures, and social networks thanks to the billions of strangers who share the planet.

After two centuries of rising population and rising prosperity, attempts to blame low living standards on overpopulation have worn thin. The most popular anti-population arguments now come from environmentalists. But their case is surprisingly weak. We’re not “running out” of food, fuel, or minerals. Despite occasional price spikes, real commodity prices have fallen about 1% per year for over a century.[11] Air and water quality in the First World have been improving for decades despite rising population.[12] Genuine problems remain, but limiting population to counter environmental problems is using a sword to kill a mosquito. Pollution taxes and congestion prices are far cheaper and more humane remedies.[13]

The most popular argument for population growth, no doubt, is that government retirement systems depend on it. Social Security and Medicare are pyramid schemes; as long as the ratio of workers to retirees is high, low taxes are enough to support the elderly in style. Libertarians might daydream that low fertility will topple the welfare state. But Americans of all ages love these programs. If they have to pay higher taxes to preserve them, they will.

The fiscal argument for population also has a catch. It only justifies the creation of tomorrow’s net tax-payers—not people per se. But the catch isn’t as binding as it looks. You don’t have to raise the average to pull your weight. Much government spending—including the military and interest on the national debt—is “non-rival”: The total cost stays the same as population goes up. To be a net tax-payer, you merely have to cover the marginal cost of the services you consume and the benefits you collect.[14]

The most neglected benefit of population growth, though, is that more people get to exist. Almost everyone is glad to be alive. Thanks to the magic of hedonic adaptation, most people around the world consider themselves happy—even when severely handicapped or mired in Third World poverty.[15] There are plenty of good reasons not to reproduce, but “It wouldn’t be fair to the child” isn’t one of them. How can it be “unfair” to give a gift so reliably better than nothing?

One can admittedly imagine negative externalities of population vast enough to outweigh all the positives. Just picture a world so crowded that there’s no room to move. But there’s no sign that the real world is anywhere close. Over the observed range, people and good outcomes go hand in hand—and there’s no sign of anything else on the horizon.

Population, Policy, and Persuasion

In a statist society, highlighting a problem sounds like a thinly veiled call for government intervention. As a result, libertarians feel a strong and often justified impulse to deny that problems exist. Occasionally, though, libertarians’ own arguments require them to take a problem seriously. Low fertility and underpopulation are two such problems.

Coercive policies to promote fertility and population growth abound. Communist Romania banned contraception to boost its birth rate.[16] Raising fertility is one rationale for Scandinavia’s “family friendly” parental leave regulations and child care subsidies.[17] French policy has been explicitly natalist since the 1930s.[18]

None of these are policies that libertarians can or should support. The decision to have a child is so personal that even nonlibertarians recoil at the prospect of applying social engineering to it. Fortunately, there are effective libertarian alternatives. Governments can boost population and fertility by repealing some especially foolish regulations and cutting some especially destructive taxes.

Relaxing or abolishing immigration restrictions is a simple, potent cure for underpopulation. At the world level, underpopulation and low fertility are roughly the same problem. But at the national level, they’re separable.[19] Every First World country can swiftly increase its population—but not its fertility—with the stroke of a pen by liberalizing immigration. A billion people on earth live on a dollar a day or less. Many, if not most, would move to any First World country willing to admit them. Doing so would also drastically increase their productivity and wages.[20]

Free immigration is the most morally imperative remedy for underpopulation. Respecting foreigners’ rights to accept job offers from willing domestic employers and rent apartments from willing domestic landlords is a matter of justice, not charity.[21] Given the benefits of population, First World countries lack even the bad excuse that immigration restrictions are in their national self-interest. But sadly, free immigration has almost zero political support. Is there any libertarian remedy for underpopulation that appeals to a wider range of political philosophies? Yes. The best available evidence implies that giving parents one-shot tax credits for every child they bring into the world would literally pay for itself.

To verify this strong claim, we need two measurements. First: What is the total “fiscal externality” of a new baby—the present discounted value of the marginal cost of all the government services the baby will ever consume, minus the present discounted value of all the taxes the baby will ever pay? Second: How much do you have to pay people to persuade them to have another child?

Because much government spending is non-rival, estimates of the fiscal externality of a new baby are positive and large. The highest-quality study is probably Wolf et al (forthcoming).[22] For the United States, it calculates a positive externality of $217,000 in 2009 dollars—roughly five times per-capita GDP.[23] [See correction, below.] Estimates of the responsiveness of fertility to cash are also fairly high. The highest-quality study is probably Milligan (2005), which carefully analyzes Quebec’s quasi-experimental baby bonuses.[24] It finds that a baby bonus of Can $1000—just 5% of per-capita GDP— increased the probability of having a child by 16.9%.[25] Since Quebec’s total fertility rate at the time was roughly 1.5, this implies roughly a .25 increase in the total fertility rate. Since you get about one additional child for every four bonuses, the total cost per child created equals 20% of per-capita GDP.

Researchers have to make many simplifying assumptions to get such simple answers. But if their conclusions are remotely accurate, natalist tax credits are a fiscal free lunch.[26] If the government can capture an income stream with a present value of $217,000 by foregoing $9000 in taxes today, who could oppose it? Libertarians and conservatives should be happy to reduce the tax burden. Liberals and moderates should be happy to improve the government’s fiscal health. Anyone who appreciates the broader benefits of population should be happier still.

Alas, as my first book, The Myth of the Rational Voter, argues, democracies often stubbornly refuse to adopt policies that no reasonable person could oppose.[27] Freer immigration and natalist tax credits are great ideas, but they probably aren’t going to happen. Fortunately, a viable apolitical remedy for low fertility and underpopulation exists. Bringing this apolitical remedy to a broader audience is a major goal of my new book, Selfish Reasons to Have More Kids.[28]

My thesis is that people underestimate not just the social benefits of having kids, but the private benefits as well. Parents emotionally overcharge themselves for kids because they overestimate the long-run effect of upbringing. If heavy parental investment and sacrifice are necessary to turn your children into successful, well-adjusted adults, being a good parent isn’t very fun—and being a good parent of a lot of kids is no fun at all. Fortunately, four decades of adoption and twin research show that high-effort parenting is greatly overrated. The estimated effect of parents on health, intelligence, happiness, success, character, and values usually ranges from small to zero.[29] This doesn’t mean that you can harmlessly abandon your child in Haiti; adoption and twin researchers study vaguely normal families in First World countries. But the diverse parenting styles within this vaguely normal range are about equally good.[30]

The immediate lesson of adoption and twin research is that parents should relax, make fewer painful sacrifices, and focus on enjoying their time with their children. But there is a deeper lesson: The kids you want are cheaper than you think.[31] And how do common sense and basic economics tell you to respond to lower prices? Buy more. Once parents let go of their unnecessary unhappiness, having another child becomes a much better deal. If that deal is good enough to tip the scales, the child, his parents, taxpayers, and the world share the benefits.

Can one book really noticeably raise overall fertility? Probably not. The world is a big place; the best of books won’t move it much. But that doesn’t mean that education and persuasion are ineffective. No single book noticeably reduced smoking rates or anti-gay prejudice, either. But decades of education and persuasion have made a huge difference. There’s no reason why education and persuasion couldn’t have equally large effects on fertility and population.

Libertarians of all people should be open to this possibility. They know better than anyone that civil society already handles most of the social problems that governments habitually ignore, aggravate, and create. Governments could boost population and fertility by admitting more immigrants and cutting parents’ taxes. But there’s no reason to wait around for governments to do the right thing. The surprising science and economics of nature and nurture is already here. Anyone who values the lessons of Julian Simon should spread the word.

Correction on Fiscal Externalities

After writing this essay, I realized that I had misinterpreted Wolf et al’s $217,000 “fiscal externality of becoming a parent” estimate (above, at note 23). Most articles in this literature estimate the fiscal externality of having a child. But Wolf et al instead estimate the total fiscal externality of being a parent instead of a non-parent. As they put it:

The difference between the NPV [Net Present Value] of the fiscal flows of parents and nonparents, i.e. NPV_P − NPV_NP + NPV_OFFSPRING, represents the fiscal impacts of replacing an average nonparent with an average parent.

A rough estimate of the per-child externality is therefore not $217,000 as I originally wrote, but $217,000 divided by (average number of children | number of children > 0). For the United States, that denominator is roughly 2.6, so the per-child externality falls to about $83,000—roughly 180% of per-capita GDP. This is still about nine times larger than the estimated tax credit the U.S. government would have to offer to induce parents to have another child.

I thank Douglas Wolf and especially his co-author Ronald Lee for timely responses to my inquiry on this point. The mistake was entirely my own.

Notes

[1] See e.g. Matthew Connelly. 2008. Fatal Misconceptions: The Struggle to Control World Population. Cambridge: Harvard University Press.

[2] Edwin Dolan’s seminal free-market environmentalist TANSTAAFL: The Economic Strategy for Environmental Crisis. 1971. New York: Holt, Rineheart, and Winston, p.64 does sympathetically entertain Kenneth Boulding’s proposal for tradable baby permits, but ends by endorsing laissez-faire.

[3] His magnum opus is Julian Simon. 1996. The Ultimate Resource 2. Princeton, NJ: Princeton University Press, a much-expanded version of the original 1983 edition. See also Julian Simon, editor. 1995. The State of Humanity. Cambridge: Blackwell Publishers.

[4] The United States had a total fertility rate of 2.1 in 2008; it has since slipped slightly below replacement. Several oil-rich Gulf states with high per-capita income also have fertility above the replacement rate, but they arguably don’t qualify as “modern economies.” For total fertility rates, see UNdata.

[5] For current and projected population data, see UNdata.

[6] On the Malthusian model, see Greg Clark. 2008. A Farewell To Alms: A Brief Economic History of the World. Princeton: Princeton University Press, pp.19-39.

[7] See e.g. David Weil. 2005. Economic Growth. New York: Addison-Wesley, pp.182-265, and Paul Romer. 2010. “Economic Growth.” In David Henderson, ed. The Concise Encyclopedia of Economics. Indianapolis, IN: Liberty Fund, pp.128-31.

[8] Besides Julian Simon’s writings, see also Michael Kremer. 1993. “Population Growth and Technological Change: 1,000,000 B.C. to 1990.” Quarterly Journal of Economics 108: 681-716, and Paul Romer. 1986. “Increasing Returns and Long-Run Growth.” Journal of Political Economy 95, pp.1002-1037

[9] Kremer 1993.

[10] On Tasmania’s less-than-zero progress, see Jared Diamond. 2005. Guns, Germs, and Steel: The Fates of Human Societies. New York: W.W. Norton, pp.312-313.

[11] Paul Cashin and C. McDermott. 2002. “The Long-Run Behavior of Commodity Prices: Small Trends and Big Variability,” IMF Staff Papers, pp. 175–199, find that the inflation-adjusted price of the Economist’s index of industrial commodities fell by about 1 percent per year from 1862 to 1999. Stephan Pfaffenzeller et al. 2007. “A Short Note on Updating the Grilli and Yang Commodity Price Index,” World Bank Economic Review 21 (1), pp. 151–163, report that, adjusting for inflation, the Grilli and Yang commodity price index (which includes metals, food, and nonfood agricultural products) fell by about .8 percent per year between 1900 and 2003.

[12] See Bjorn Lomborg. 2001. The Skeptical Environmentalist: Measuring the Real State of the World. Cambridge: Cambridge University Press, pp. 163–177, 189–205.

[13] See e.g. Alan Blinder. 1988. Hard Heads, Soft Hearts: Tough-Minded Economics for a Just Society. New York: Basic Books, pp.136-159.

[14] Worth noting: Top-heavy age pyramids would remain a problem even if government got out of the retirement business entirely. Imagine what would happen if everyone stopped having kids. In three generations, we’d all be “retirement age.” But what would your retirement savings buy in a world with a worker/retiree ratio of zero? Most of us would wind up spending our sixties and seventies working for people in their eighties. The point is not that this nightmare is likely, merely that under laissez-faire, retirees’ quality of life continues to depend on the fertility of younger generations.

[15] See Frederick Shane and George Loewenstein. 1999. “Hedonic Adaptation.” In Daniel Kahneman et al, eds. Well-Being: The Foundations of Hedonic Psychology. New York: Russell Sage Foundation , pp.302-329.

[16] Charlotte Hord et al. 1991. “Reproductive Health in Romania: Reversing the Ceausescu Legacy.” Studies in Family Planning 22, pp.231-240.

[17] See e.g. Anders Björklund. 2007. “Does a Family-Friendly Policy Raise Fertility Levels?” Swedish Institute for European Policy Studies 3.

[18] Claude Martin. 2007. “A Baby-Friendly State: Lessons From the French Case.” Pharmaceuticals Policy and Law 9, pp.203-210.

[19] If you take Simon seriously, liberalizing immigration sounds like a “beggar-thy-neighbor” policy. Doesn’t the sending country lose the positive externalities that the receiving country gains? There are however two mitigating factors. First, since relocation increases a worker’s income, it makes his positive externalities more positive. Rich consumers do more than poor consumers to foster innovation, expand choices, and share fiscal burdens; creators are more likely to realize their potential in the First World than the Third. Second, migrants return much of their new-found wealth to people in their home countries as remittances. Some positive externalities of population hinge on physical proximity; but thanks to modern communication and transportation, the whole world benefits when an immigrant moves from the Third World to the First.

[20] See Michael Clemens, Claudio Montenegro, and Lant Pritchett. 2008. “The Place Premium: Wage Differences for Identical Workers Across the U.S. Border,” Washington, DC: Center for Global Development Working Paper #148.

[21] See Michael Huemer. 2010. “Is There A Right to Immigrate?” Social Theory and Practice 36, pp.249-261.

[22] Douglas Wolf et al. forthcoming. “The Fiscal Externalities of Becoming a Parent.” Population and Development Review.

[23] 4.7 times to be more precise.

[24] Kevin Milligan. 2005. “Subsidizing the Stork: New Evidence on Tax Incentives and Fertility.” Review of Economics and Statistics 87, pp.539-555.

[25] Milligan finds that responsiveness varies with pre-existing family size. The 16.9% figure is the estimated responsiveness for people who already have one child.

[26] There is at least one major reason to think that natalist tax credits are better than simple estimates suggest. Quebec’s program paid baby bonuses to everyone. My proposal, in contrast, only rewards parents who actually pay taxes. Since income runs in families, the extra children born are especially likely to be net taxpayers.

[27] Bryan Caplan. 2007. The Myth of the Rational Voter: Why Democracies Choose Bad Policies. Princeton, NJ: Princeton University Press.

[28] Bryan Caplan. 2011. Selfish Reasons to Have More Kids: Why Being a Great Parent Is Less Work and More Fun Than You Think. New York: Basic Books.

[29] Caplan 2011, pp.37-91.

[30] There are exceptions to the rule that nurture doesn’t matter much. Parents do have strong effects on the religion and political party you say you belong do. But this influence is fairly superficial: Nurture matters much less for religious doctrines, issue positions, church attendance, and voting. (Caplan 2011, pp.62-66) Parents’ most meaningful effect is on kids’ appreciation – how they feel about and remember their parents. A study of older Swedish twins confirms that this really does last a lifetime. (Caplan 2011, pp.71-72) The haunting lesson: Struggling to perfect your kids isn’t just fruitless; it can easily backfire by hurting the parent-child relationship.

[31] Caplan 2011, pp.84-91.

Bryan Caplan offers a sprightly defense of population growth. Middle class Americans should discard two entrenched prejudices that keep their families small. Children are costly to the world at large. And they are tiresomely and endlessly burdensome to parents.

Children impose not costs, but benefits, on the rest of society. And children can be raised to be prosperous citizens with only modest parental care.

I think Caplan’s first proposition will soon prove to have applied only in a limited historical window. Future population increases will likely exert substantial downward pressure on the growth of living standards.

But he is right that the U.S. middle class dramatically overestimates the benefits of parental inputs for children. Since there are positive social benefits from middle class children, higher fertility by this group would be a social benefit.

Are People the Ultimate Resource?

Caplan’s empirical evidence on this is merely that since 1800 world population has increased 7 fold, to 6.7 billion, while incomes per person have also increased.

But that historical fact tells us nothing about the future effects of population on incomes. If by 2050 the projected 9 billion people in the world all have just current U.S. consumption standards, then we must produce 8 times as much oil as now, and 5 times as much food. In that world will population levels still not matter?

Population growth always generates gains and losses. More population drives up the cost of limited resources: land, minerals, and fossil energy. But larger populations reduce production costs through scale economies. Think Walmart. And more people increase rates of technological advance by multiplying the stock of potential innovators.

There is thus a race between resource costs and scale economies as population grows. And the crucial factor that determines the strength of these effects is just the share of land and mineral rents in national income. Before 1800 that share was substantial: 20-25%.

Thus for 99.9% of human history, up till 1800, the winner in that competition was resource scarcity. We see this clearly in the onset of the Black Death in Europe in 1347-8. England, for example, had a population of 5 million in 1347. By 1450 recurring waves of plague slashed that to 2 million. England then was reduced to isolated pockets of people (England now has 51 million). The population collapse thinned markets and trade. But living standards rose dramatically, rising to nearly triple the level of 1347, because food and energy became fantastically cheap and abundant. Indeed England did not again equal plague year living standards until 100 years after the onset of the Industrial Revolution.[1]

Similarly the doubling of population in England 1540-1620 may have helped produce Bacon, Shakespeare, and Marlowe. But it also halved living standards.

The reason population had so little effect on income 1800-2011 is that technological advance made food and energy much cheaper over these years, driving down the land and mineral rent share to less than 5% worldwide.

The figure below shows, for example, shows the hours of work required to buy the energy equivalent of a gallon of gas in England from the 1260s to the 2000s. Workers today can buy a gallon of gas with the earnings from 20 minutes of work. In the 1960s and earlier that took four hours.

Energy Costs Relative to Wages, England, 1250-2000

Demand for food and energy grew more slowly than supply 1800-2011 for several reasons.

• Only a small fraction of the world grew rapidly. The living standards of 2 billion Indians and Chinese in 1990, for example, barely exceeded pre-industrial levels. The West thus was alone in its voracious appetite for raw materials and energy. India, for instance, by 1900 had become mainly a raw material exporter: wheat, jute, cotton and tea.
• There was a huge expansion of the cultivated acreage—new lands were opened in the Americas, in Australia and New Zealand, and in southern Africa.
• Fossil fuels cheaply substituted for farmland by increasing yields.

But now, with much of the energy and mineral reserves of the West depleted, China and India instead of supplying food and energy to the world economy have become frantic importers. The supply of new lands is largely exhausted. In addition fears of global warming, and equal fears of nuclear energy, have added a new burden of bio-fuel production to land in the U.S., Brazil and the EU. The U.S. alone plans producing 30 billion gallons of bio-fuel annually by 2022, implying trebling corn output.

To feed a world of 9 billion by 2050 living at U.S. consumption standards would require food yields per acre worldwide to grow 4% per year between now and then. There is room for substantial catch up in yields in the Third World with those in the West. But once that happens the prospect of continued rapid expansion of output is poor. In the UK, for example, the total output of the farm sector is no higher now than in 1984.[2] This will force up food and energy prices, raising the share of land and resource rents in total incomes.

So the downward march of food and energy prices since 1800 may well end soon. Current high prices may presage a food scarce-energy scarce future. If this causes the share of land and mineral rents in economies to again become significant, then we will have Malthus Redux. Population will again be an important determinant of income.[3]

This implies a negative externality associated with fertility, with all the unpleasant implications this holds for those of libertarian persuasion.

How costly are children to parents?

I find convincing Caplan’s argument that the modern middle classes have wildly overestimated the value of constant parental attention in raising the quality of their children. Genetics plays a much greater role in child outcomes than the average middle class parent believes. Indeed perhaps the major parental contribution is made by the time of conception.

What is surprising, however, is the grip that “the nurture obsession” has on the modern middle classes. There is plenty of evidence around for everyone to see that nurture is not determinative of outcomes. So why is this such a deep rooted and unquestioned belief?

I can add, however, some historical work (done with co-author Neil Cummins of CUNY Queens) in support of the Caplan contention.[4]

In this work we look at the social mobility of a group of rich and poor people with rare surnames in England over five generations between 1858 and 2011. The rich of the first generation had significant wealth, lived much longer, and with high frequency attended the elite universities, Oxford or Cambridge. The poor had no wealth, lived short lives, and none of them had attended Oxford and Cambridge.

Even four generations later these groups are still distinct. The descendants of the rich group are twice as wealth on average, live four years longer, and were twice as likely to be students at Oxford or Cambridge.

But they have clearly moved much closer in status with each generation. And they are clearly destined within 3-4 more generations to both converge on average social status. There is eventual regression to mediocrity for both rich and poor.

However slow it is, the fact that these two groups from the opposite ends of the social spectrum eventually converge is one of compelling interest. What makes this happen? Throughout these generations the rich have fewer children than the poor. With their resources, and with fewer children to nurture, why did they not form a permanent upper class? Why were they eventually dragged down to the average? Similarly how did the poor get themselves towards the average, starting as they did with no wealth, and larger families?

If we posit that nurture is destiny then this process defies explanation. Societies should be divided forever into upper and lower classes.

But if we posit that the most important element in the fate of families is genetics, we can perfectly well understand these processes. The achieved social status of families is a phenotype, stemming from some underlying genotype plus some random error. If men and women mate, as they must, based on the observed phenotype, then there will be an inherent tendency of those above and below the mean to mate with those whose genotype is closer to the mean, and to thus produce children closer to the mean. Francis Dalton, in his study of the inheritance of stature in the nineteenth century, explained the phenomena of regression to the mean in heights in exactly such terms.

So a challenge to anyone who would doubt Caplan’s claim that nature is much more important than nurture in the outcomes for children is to account for the above observation of eventual regression to the mean. Why must the few and pampered children of the elite eventually have offspring who return to the mean if the circumstances of our upbringing are the major determinants of our success in life? How do the abundant and neglected children of the poor eventually rise to average status if again nurture is the crucial determinant of life success?

Notes

[1] For more on this see Gregory Clark, A Brief Economic History of the World, chapters 2-3.

[2]Output per worker has grown substantially in this period, but not output per acre. http://www.defra.gov.uk/statistics/foodfarm/cross-cutting/auk/, table 10-1.

[3] This is not to imply that these constraints will reduce income, just that population growth will once again slow income growth rates significantly.

[4] See http://www.ehs.org.uk/ehs/conference2011/Assets/ClarkFullPaper.pdf

There is much I can agree with and even admire in Bryan’s essay. Having frequently clashed with Malthusians, it is refreshing to read such a fresh and enthusiastic argument for why we should welcome every new addition to the human family. And, as a new father, I am relieved to hear that I can stop worrying and just let my toddler run amok. She will thank you for it, Bryan, right up until the point that she breaks her collarbone. But I fear that over the long run puppies, breakables, and younger siblings may be somewhat worse off.

Still, we must not use the future as evidence. Population projections, technology forecasts, and dire scenarios about what happens when we run out of this or that have been an extremely poor guide to policymaking. Too often, scary predictions turn out to be spurious, but inspire even more terrifying reactions that have real and demonstrable costs. One of the great strengths of Bryan’s essay is that it is rooted in historical evidence rather than mere speculation about the future.

My problem is that it does not go deeply enough into the history of population panics and the reactions they have provoked, as shown in its very first line. People have been fretting about babies for thousands of years. And for almost all of recorded history, population growth was seen as indisputable proof of prosperity, rather than the reverse. The world’s largest religions all encourage people to be fruitful and multiply. When they have succeeded, it was seen as a measure of sound laws and good government, and states took pride in seeing their numbers grow. When governments began to notice the decline of fertility, most reacted with alarm—recall Teddy Roosevelt’s despair over “race suicide.” Political and religious authorities worked together to deny people access to contraception and keep abortion unsafe and illegal. Even in Britain, the native land of Thomas Malthus, Malthusianism was a fringe movement until the mid-twentieth century. Even then, many governments insisted that their problem was not too many people, but too few.

State policy and social pressure have therefore favored large families for most of history, and continue to do so in many parts of the world. To start this story in the 1960s therefore gives a very misleading impression, in which pro-natalists appear like the natural ally of libertarians. In fact, up until that point people like Margaret Sanger who championed the right to contraception were about the only people who defended individual’s right to have as many children as they wanted. And when some of them—including Sanger—began to argue that people had not only a right to contraception, but a positive duty to plan their families, their main opposition continued to be those who believed that Malthusianism was contrary to the prerogatives of religious or governmental authority—especially Catholics and Communists.

The Catholic hierarchy was not just troubled by the moral aspects of allowing people to have sex without having children. They also worried that women who could control their own bodies would be less likely to obey their husbands and remain loyal to the Church. With the coming of state population control policies aimed at engineering specific population outcomes, beginning with eugenic programs to sterilize the “unfit,” Church leaders were stalwart in opposing what they deemed to be government interference in personal matters of faith. But they voiced no opposition to a eugenics program that aimed at encouraging “fitter” parents to have ever larger families. The Church defended—and continues to defend—state laws that limit or preclude access to birth control and abortion.

Communists opposed Malthusianism for attributing poverty to the misguided choices of poor people. It also undermined the idea that people working together could eradicate poverty, providing a powerful rationale against redistributive policies. This is why Marx considered Malthus a mortal enemy. Like libertarians, his followers insisted that Malthus had slandered humanity by underestimating people’s capacity to create and produce when freed of oppression. Even so, Communist countries could quickly change population policies depending on the needs of the state. The Soviet Union was the first country to provide birth control and abortion in government clinics, but once war with Germany loomed on the horizon Stalin withdrew contraceptives from the market, banned abortion, and paid mothers cash incentives to bear large families.

What this history suggests is that even when a desire to increase family size is rooted in ideological commitments—even in commitments that are as strong and dogmatic as Catholicism and Marxism-Leninism—pro-natalists can be quite opportunistic in pushing one or another means to that end. And they have been very willing to use the coercive power of the state when mere persuasion is unavailing. This has been true even when specific measures, such as denying access to condoms—even for those with HIV/AIDS—run entirely contrary to Catholic values of charity for the poor and mercy for the afflicted. And Communists have been quite willing to jettison an ostensible commitment to gender equality when the Party decided it needed women to breed more soldiers.

Clever economic theories about paying people to have more or fewer children—which attempt to reduce existential questions about the meaning and value of life to statistical regressions—have led to even more opportunistic, manipulative, and coercive policies. It was economists who calculated the incentive payments they thought would persuade poor people to be sterilized, estimating the net benefit to society of each “birth averted.” This is actually how Julian Simon started out in the field. But in India and other countries these payments had the most perverse effects. It was often grandpa and grandma who showed up at the clinic and did their bit to support their families. And when World Bank economists suggested paying poor women to have IUDs inserted, they had them inserted—and removed—over and over again. That is when Indira Gandhi decided to suspend civil liberties, pull people off of buses, and drag them to sterilization camps.

Most people who study pro-natalist incentives find that they have very little effect on fertility. What happens when all the economic arguments indicate we need more people and couples once again fail to respond to incentives? What happens when, because we have some new queen of the social sciences, higher order math indicates that it would be cheaper and easier to clone “net taxpayers” in laboratories, or even cull older people who cannot meet their marginal costs?

It is difficult to control population absent coercion, and even then the results tend to be unpredictable if not pernicious—witness the male-female ratio in China following the one child policy. People are stubborn in their beliefs and behavior when it comes to childbearing. Moreover, we do not have a theory that can explain, much less predict, why that behavior changes over time. In other words, economists do not know where babies come from. And without a theory for fertility, we do not know how to manipulate it.

History suggests that, however alarming population trends may sometimes seem, and however alluring the idea of a quick fix, we will pay dearly if we do not maintain an absolute commitment to reproductive rights. State policies to pressure people to have more or fewer children can have long afterlives, and may contribute to social pressures that can also be quite oppressive. If you wonder why there is so much pressure to produce perfect children—beginning with genetic testing, and ending with the college admissions madhouse—recall how pervasive and popular eugenics was when today’s grandparents and great-grandparents first came of age.

Libertarianism does not represent a commitment to large or small families, or even to increasing wealth, but rather to defending individual liberty. Now that fertility rates are falling in almost every country, libertarians need to be mindful of this longer trajectory and think carefully about where an alliance with pro-natalism might one day lead.

Much of the discussion so far has focused on Caplan’s argument that more people are good for society. I want to focus on the second claim: parents are unhappy because they put too much pressure on themselves to be perfect parents.

Parents are Unhappier

Caplan is definitely right about the first part: Parents are unhappy. I’ve checked, and for every subgroup of the population I analyzed, parents report being less happy than similarly situated nonparents.[1]

Three years ago I was trying to chart my own life course, and—ever the empiricist—thought the data might be helpful. While I knew the reports about unhappy parents, I thought that perhaps my demographic may be different. And we are—a bit. The average happiness of parents who have higher incomes and are older is lower than comparable nonparents. But the happiness gap between these nonparents and parents is much smaller than the parental happiness gap among those that are younger and have lower incomes. Bear these facts in mind, as we turn to asking which parents are putting too much pressure on themselves.

Is Over-Investing in our Children the Cause of Parental Unhappiness?

Caplan suggests that over-investing in kids explains why parents are unhappy. Here’s a simple test of his hypothesis: Are the parents who are most unhappy (relative to their peers) the same folks who are over-investing? The answer appears to be no.

Time-use data suggests that it’s college-educated parents who are most likely to be over-investing: they spend more time on childcare and have vastly increased the amount of time they spend on childcare over the past two decades.[2] But recall that these aren’t the parents who have much lower happiness compared to similar nonparents. Moreover, recent cohorts of college-educated moms—the ones who have increased the time they spend on children the most—take much less of a happiness hit from having kids. The happiness gap between college-educated nonmoms and moms has been shrinking over time.

Why the increase in happiness when childcare time is increasing? College-educated parents are more likely to spend time with their kids with their spouse present.[3] Perhaps college-educated moms aren’t overinvesting in the chore called childcare, but are instead having more of the leisure called family time.

Or Are We Under-Investing in Relationships?

So we’ve figured out that parents who are younger and have less income and education are the most likely to be less happy than their nonparent peers. You don’t need a fancy theory of over-investment to explain their unhappiness. For these groups parental unhappiness may just reflect the challenges of providing food, shelter, care, and education for their kids. Meeting these very real needs can cause very real stress, particularly when the tradeoff that parents often face is caring for themselves, their spouse, or their child.

And it may be that it’s the spouse who loses out. When couples have children their relationship often suffers. In fact, parents are about 15 percent less likely to report that their marriage is “very happy” than similarly situated nonparents.[4]

There’s More to Life than Happiness

Even if Caplan’s theory fit all the happiness and time use facts, so what? Happiness is just one aspect of a good life. Perhaps our kids decrease our happiness, but increase our fulfillment. If so, parents are less happy, but they are not worse off for having kids. This distinction between happiness and fulfillment animates a debate among happiness researchers: Does happiness capture our total well-being—in economics-speak, our “utility”—or is there something more? The first generation of happiness researchers equated happiness with utility. But the second generation disagrees, arguing that happiness is just one component of a good life.

Nobel Prize–winning economist Gary Becker, writing with Luis Rayo, has argued this contrary position. In their view, while “happiness and life satisfaction may be related to utility, they are no more measures of utility than are other dimensions of well-being, such as health or consumption of material goods.”[5] Or having kids. Children may make you less happy, but still raise your utility. Devout neoclassical reasoning leads Becker and Rayo to infer from the fact that we are having kids that they raise your utility (or at least they raise the utility of those who make this choice).

OK, so this line of reasoning comes awfully close to making economic reasoning perfectly circular. So let’s return to asking: If there’s a mistake, what is it?

Are the Returns to Investing in Our Children Really So Low?

Caplan’s key evidence for the proposition that we are over-investing in our children comes from twin studies that he interprets as showing that parents have little effect on the outcomes of their children. Yet the evidence isn’t quite as clean as he suggests. Many studies have shown that adults are extremely important in early childhood and that the returns can be quite high. One recent prominent study found that students with a more experienced kindergarten teacher earned an extra $1,000 at age 27 relative to students who had been randomly assigned a less experienced teacher.[6] If that’s the effect of one teacher for one year, surely the effects of two parents for many more years will be much larger.

We know that the benefits of extra resources can be substantial and greater than the costs for poorer children. Jim Heckman has spent years documenting the facts, and he says quite states starkly that “Parenting matters,” continuing that “the true measure of child advantage and disadvantage is the quality of parenting received.”[7]

As much as we can debate the facts, none can speak directly to Caplan’s claim that we are over-investing in our children. Even if the returns are low, who is an econometrician to say that they aren’t high enough for me? And who is to say that they aren’t high enough for other parents? Where’s consumer sovereignty in all this?

The Quality-Quantity Tradeoff: It’s More Complicated

Let’s take stock. Caplan suggests that parental over-investment in their children is causing parents to be unhappy. He infers from this that we should invest less in each child, and have more children. In the classic quantity-quality trade-off, Caplan is arguing that too many resources are going to child quality and not enough are going to child quantity.

Stating the problem this way makes it clear that Caplan’s argument actually requires parents to be making two mistakes. The first mistake is that the returns to the marginal hours with our children are lower than we think, and so we are over-investing in quality. If he’s right, we can all save ourselves a lot of time. But this doesn’t mean that we should necessarily have more kids. Here’s where the second assumption really matters: Caplan thinks that we should take the time we save and spend it on a greater quantity of children.

You can think of this another way. Caplan says that we parents are charging ourselves too much for children. And just as we buy more televisions when the price falls, we should have more children when the price falls.[8] Maybe. But maybe not. When we reduce the price, there are both income and substitution effects. Caplan is entirely focused on the substitution effect: having kids becomes cheaper relative to buying TVs. So he says buy more kids, and fewer TVs. But what about the income effect? As people become richer, they tend to “buy” fewer children, not more. So there’s an offsetting income effect. Is it possible that the income effect overwhelms the substitution effect? Typically this only occurs among goods which take a big share of our budgets. Like children.

Concluding thoughts

Let’s put aside debating the facts for a moment, and just focus on their implications. Even if Caplan is right that further investments in child quality yield little payoff, this doesn’t mean that we should have more kids. If kids are making us unhappy, perhaps we would simply choose to invest less in our kids and more in our own happiness.

But this leads me back to trying to understand why kids are correlated with unhappiness instead of happiness. In my own life my daughter has brought me enormous joy and happiness. And this is despite the fact that I may even over-invest in her. But I’ve avoided many real and difficult trade-offs by planning and preparing to become a parent at a time when it worked best for me and my partner. Is parental choice the key to parental happiness? I don’t know. But what I do know is that I would want to know more about what makes parents unhappy before I told anyone that I thought they were making a mistake by having too few children.

Notes

[1] This result compares people surveyed in the General Social Survey between 1972 and 2008 and controls for differences in age, education, income, race, religion, and marital status.

[2] Ramey, Garey and Valerie Ramey, “The Rug Rat Race,” Brookings Papers on Economic Activity, Spring 2010.

[3] Dan and Betsey Stevenson “‘The Rug Rat Race’: Comments and Discussion” Brookings Papers on Economic Activity, Spring 2010.

[4] This is the result of a regression analysis using the General Social Survey, controlling for ages, race, income, education, and religious backgrounds.

[5] Becker, Gary and Luis Rayo, “’Economic Growth and Subjective Well-Being: Reassessing the Easterlin Paradox’ : Comments and Discussion,” Brookings Papers on Economic Activity, Spring 2008, pp. 88-95.

[6] Chetty, Raj, John Friedman, Nathaniel Hilger, Emmanuel Saez, Diane Whitmore Schanzenback, and Danny Yagan, “How Does Your Kindergarten Classroom Affect Your Earnings? Evidence from Project Star,” forthcoming Quarterly Journal of Economics.

[7] Heckman, James “The American Family in Black and White: A Post-Racial Strategy for Improving Skills to Promote Equality,” National Bureau of Economic Research Working Paper No. 16841, March 2011.

[8] Caplan, Bryan, “Parents: Stop Overcharging for Your Kids” WSJ Blog April 13, 2011.

Greg Clark freely admits that the last two centuries have been wonderful for mankind. But will current trends continue? Clark suggests that they won’t. Growth is a “race between resource costs and scale economies as population grows” and “for 99.9% of human history, up till 1800, the winner in that competition was resource scarcity.” This seems like a telling point: Shouldn’t we base our predictions on all the data instead of the most recent .1% of it?

But how far is Clark willing to take this? The last two hundred years have been unprecedented in countless ways. Population, per-capita income, technology, science, literacy, culture, democracy, lifespan, and international trade exploded. Slavery, monarchy, and death from infectious disease withered away; war itself is poised to join them. Does Clark really expect long-run historical norms to reassert themselves in most of these areas? When you compare the last .1% of human history to the previous 99.9%, there really appears to be a structural break. You don’t have to understand the underlying model to accept this brute fact.

But we can do much better than merely insist, “The modern world is different.” Contrary to Clark, my target essay didn’t merely observe that population and per-capita living standards both sharply increased over the last two centuries. Instead, I built on two widely accepted claims. First: New ideas are the main driver of economic growth. Second: Higher population increases both the supply and demand for new ideas.

Clark is right to name economies of scale as one social benefit of population. But he neglects the far more important effect on innovation. The technological advance that Clark credits for rising abundance of food and energy didn’t come out of thin air; it came from people. If the Black Death had never happened, there is every reason to think that the modern world would have arrived centuries earlier.

A few challenges for Clark:

1. You think one important reason why food and energy grew cheaper in the modern era is that “Only a small fraction of the world grew rapidly.” But if you look at your own graph, the downward trend continues long after economic growth spread to most of the rest of the world.

2. “The supply of new lands is largely exhausted.” This is factually mistaken. In the United States alone, only about 20% of available land is used for growing crops.[1] This percentage has been roughly constant since the 1930s—not because no other land suitable for farming exists, but because conversion of forests to farmland has been roughly balanced by conversion of farmland to forests.

3. Negative externalities of fertility? Even in a Malthusian world, population is not analogous to air pollution. Suppose we literally lived in a zero-sum world. As long as parents are financially responsible for their children, any negative effect of population on living standards is internal to the family. As Landsburg explains:

When people think about overcrowding or overpopulation, they typically imagine that if, for example, I had not been born, everyone else would have a slightly bigger share of the pie. The truth is that if I had not been born, both of my sisters would have substantially bigger shares of the pie and everybody else’s share would be pretty much the same as it is now.[2]

In other words, the negative externalities, if any, are intra-family. If parents didn’t care about their already existing children, or if children didn’t value siblings, there might still be a problem. But parents do care about their already existing children, and at least many children value having siblings. So it’s unclear whether a problem even exists.

4. Are you actually willing to bet that global real per-capita GDP will be lower in 2020 than it is today? How about 2030? 2050? If you’re willing, let’s hammer out a deal. If you’re not, it looks like I’m not the only one who finds the last two centuries a more reliable guide to the future than the preceding two hundred millennia.

Notes

[1]See H. Thomas Frey, “Trends in Land Use in the United States.” In Julian Simon, ed. 1995. The State of Humanity. Cambridge: Blackwell, pp.434-411.

[2]See Steven Landsburg. 1997. Fair Play. New York: Free Press, p.150.

I have three main challenges for Matthew Connelly:

1. As far as I can tell, Connelly doesn’t deny that fertility is good. But he’s afraid of the consequences of admitting that fertility is good. After all, won’t governments take advantage of this admission to do great evil?

On Connelly’s logic, though, it seems like libertarians should be afraid to say that anything besides liberty is good. Take prosperity. As soon as you say that “prosperity is good,” plenty of statists will leap to advocate state action to increase prosperity. And to say that “pro-prosperity has a checkered past” is a vast understatement. In a twisted sense, you could call the entire Marxist movement “pro-prosperity”—their policies were a disaster, but the rationale for those policies was to make their people prosperous. We can tell analogous stories about health, literacy, technology, civility, and all the other fruits of civilization. Should libertarians be afraid to praise these as well?

I don’t think so. It’s just not reasonable to deny the goodness of prosperity, health, literacy, technology, civility—or fertility. And in any case, it’s strategically foolish. People will question liberty long before they’ll question prosperity. The wise response for libertarians is to accept the goodness of the ends, but argue that:

(a) liberty better promotes these ends;

(b) there is a trade-off between ends; and/or

(c) liberty is an important moral side constraint on the pursuit of these ends.

These replies obviously won’t convince everyone. But they’ll be at least as convincing to the typical natalist as they are to the typical proponent of economic growth.

2. Even taking the totality of human history into account, the abuses of anti-natalism swamp the abuses of pro-natalism. In the pre-modern era, there was social pressure to have more children, but there wasn’t much that government could do about it. Once modern contraception came along, Connelly is right to fault governments for banning and regulating it. But this seems relatively minor compared to the horrors of, say, India’s forced sterilization programs. Encouraging “the fit” to have more children seems minor compared to forced sterilization of the “unfit.” Even Stalin’s coercive natalism seems minor compared to the horrors of China’s One-Child policy. Does Connelly really disagree?

3. I’m puzzled by Connelly’s claim that “Most people who study pro-natalist incentives find that they have very little effect on fertility.” I had no strong preconceptions about this elasticity when I began my research. But on my reading the literature finds noticeable effects.[1] Intuitively, it looks like incentives have little effect on the fertility of younger, single women, whose pregnancies are usually unplanned. However, older, married women are much closer to the margin; moderate cash incentives are often enough to tip them over the edge.

Note

Besides Kevin Milligan. 2005. “Subsidizing the Stork: New Evidence on Tax Incentives and Fertility.” Review of Economics and Statistics 87, pp.539-555, and the literature Milligan cites, see also Rafael Lalive and Josef Zweimüller, “How Does Parental Leave Affect Fertility and Return to Work? Evidence from Two Natural Experiments,” Quarterly Journal of Economics 124 (3) (August 2009), pp. 1363–1402; and Anders Björklund, “Does a Family-Friendly Policy Raise Fertility Levels?” Swedish Institute for European Policy Studies 3 (April 2007).

Thanks to Betsey for her thoughtful reply. I already discuss some of her main points in Selfish Reasons to Have More Kids, but this is a great chance to consider them in greater detail. Let me focus on five distinct points.

1. Betsey’s reply is extremely careful, with one exception—the title. Parents are indeed unhappier, but I doubt that Betsey wants to claim that parents are unhappy in any absolute sense. In the General Social Survey, for example, the happiness gap between the married and unmarried is vastly greater than the happiness gap between parents and non-parents—and I doubt Betsey would write a piece titled “Singles Are Unhappy. But Why?”

2. My own research confirms Betsey’s first key point: Higher-income and older parents have a smaller happiness deficit.[1] And she is correct to claim that these are precisely the parents most likely to invest heavily in their kids. Nevertheless, we wouldn’t be so quick to conclude that over-investment is painless. Studies of momentary happiness do confirm that childcare feels like work—and Betsey is one of the very few parents I’ve encountered who suggests otherwise.[2] The most natural interpretation of Betsey’s finding, then, is that over-parenting is positively correlated with better finances, better preparation, better coping skills, and/or other advantages that more than compensate. My prediction is that parents who combine these advantages with a less laborious parenting style will have an especially small happiness deficit – or perhaps even a happiness surplus.

3. I completely agree with Betsey that happiness is just one aspect of a good life. But this point actually strengthens my argument. If we maximize happiness alone, then potential parents who know the science might say, “Sure, parents are unhappier than they need to be. But until you show that parents are actually happier than non-parents, I’ll remain childless.” But if we maximize a weighted average of, say, happiness and kids, then all you have to do to tilt the scales in favor of child-bearing is show that kids cost less happiness than you thought.

4. Betsey is correct to point to a few well-publicized experiments finding substantial effects of early childhood intervention programs on adult outcomes. But the adoption and twin evidence is (a) much more extensive, and (b) much more relevant for parents.

5. I agree that cutting the price of kids has both substitution and income effects. But I have trouble seeing any non-circular reason why we should expect parents’ income effect to offset their substitution effect instead of compounding it. In the General Social Survey at least, family size is increasing in income after controlling for education—suggesting that elite values, not high income per se, drives the raw negative correlation between income and number of children. If you’re willing to consider more ethnographic evidence, I’ve noticed that parents who don’t want more kids are about equally likely to invoke an implicit substitution effect (“It’s too much work to have another kid”) or an implicit income effect (“I’m too tired to have any more kids”).

Notes

[1] Caplan, Selfish Reasons to Have More Kids, pp.31-32 points out the fact that higher-income parents have a smaller happiness deficit, but doesn’t mention the parallel finding for older parents. I was however aware of both results.

[2] See e.g. Caplan, pp.16-19 for a discussion of the proper interpretation of Kahneman et al. 2004. “A Survey Method for Characterizing Daily Life Experience: The Day Reconstruction Method,” Science 306, pp.1776-1780.

Bryan Caplan has four main rejoinders to my argument that there may soon be once again a significant negative population externality:

(1) If I am confident there will soon be a negative population externality would I like to bet on when income per capita will start declining? 2020, 2030, 2040?

(2) Land is still superabundant in the United States; most is not used for farming.

(3) Suppose there were a negative population externality. Then, adopting an argument of Steven Landsburg, it would occur only within the family. The other children will be made poorer.

But the future income of the children other families will not be affected. So parents alone can decide on their optimal family size taking this into account. No one else will be affected by their decision.

(4) I have neglected the positive externality from more people through the faster production of knowledge. Growing world populations are a key factor in explaining the final appearance in the world two hundred years ago of consistent technological advance.

My responses are as follows:

(1) Income per capita will not fall in the future, even with continued population growth. Here Caplan has misinterpreted the claim I made. A negative externality associated with population is quite compatible with the continued rise in incomes. I did not mean to imply that the rise in incomes since 1800 need end if population keeps growing.

Suppose technology continues to improve by about 1% per year, as it has done for the past 200 years. That will lead to a growth rate of incomes per capita, absent population externalities, of 1.3% per year because of induced capital accumulation.

The population drag on income growth will be the population growth rate multiplied by the share of resource rents in income, times 1.3% for induced capital decumulation. Currently with natural resource rents a very small share of world income, and population growth rates of 1% of less per year, that drag is trivially small. It could easily be completely countered by economies of scale from larger populations (including economies in knowledge generation).

However if the resource rent share rose to be the 20–25% that was typical of the world before 1800, and population was to grow at 1% per year, then the population drag on income growth would rise to 0.3% per year. Incomes would rise significantly more slowly.

But for the population drag to lead to income declines would require either an impossibly fast population growth rate of more than 3%, or a rise in the resource share in incomes to close to 100%.

So the issue here is not whether incomes will in the future decline because of population growth. That will not happen at current rates of technological advance. It is whether population growth comes to be a significant drag on future income growth.

(2) Farmland is still very cheap in the United States. A recent investor newsletter talked breathlessly of land in Iowa selling for as much as $8,200 per acre. This implies a rental value of only about $240 per acre. That is not a lot of Caramel Frappucinos for a year’s use of the rich soils of Iowa.

The recent rise in farmland prices may not, however, be as transient as most past increases. Perhaps it is the beginning of a new era of land scarcity.

So if Bryan wants to bet even odds that farmland prices will be higher relative to average wages in 30 years time, I am happy to accommodate him. After all with the impending rise in world population to 9 billion people, surely given his views on population and innovation, one of these extra people will end forever the issue of land scarcity!

(3) I do not have a copy of Landsburg’s book with me, but I presume his idea is that the reduced land and resources per child that population growth implies will be felt through the amount of land and resources that each child inherits from their own parents.

The flaw in this argument is that the population externality, if it exists, is a reduction in wages for other members of a cohort which is not fully compensated by a rise in resource rents. That reduction falls almost entirely outside the family. Caplan’s kids are potentially reducing my kids’ earnings.

Since a half of families own no assets in most societies, population externalities would be sure to hurt them. So if there is a significant population negative externality there is no easy fix for your libertarian conscience through the Landsburg defense.

(4) On the claim that more knowledge growth results from having more people, I was including the effect of more people on idea production under the general category of economies of scale, since it is just another aspect of economies of scale. I was just skeptical about how significant these effects are.

Caplan has no such skepticism. “If the Black Death had never happened, there is every reason to think that the modern world would have arrived centuries earlier.”

The theoretical case for some positive effects of population on idea production seems compelling. The strength of this effect, and whether it is great enough to counteract the costs of population growth, is another matter.

It could be that there are only a fixed set of possible technological developments available to society at any time, given the existing knowledge. With this set of ideas, once we attain a certain minimum population size, all the available discoveries will be harvested. Doubling the population will just result in duplicated efforts.

Take a concrete example, Hollywood movies. Suppose we were to double the number of scriptwriters and production crews in LA. Would that double the number of innovations in movie stories and types? Or would it instead result just in Die Hard 6, Die Hard 7, and Die Hard 8 all coming out in one year?

One thing that may matter is not just the number of people, but also their living standards. In that case population growth that simultaneously has negative effects on the rate of growth of income might well also slow the rate of innovation.

Here there are too many theoretical possibilities to make theory much use. It is empirical evidence that matters.

But the empirical evidence population on idea production is weak, especially once we move to population sizes beyond those of remote island communities. If population externalities were such a sure cure for stagnation, why no Industrial Revolution in China by 1 AD, or 1000 AD?

Bryan does not deny that there is a huge problem with his entire approach: we do not know how to explain or predict fertility change. Without understanding what drives fertility, we do not know how to control it—at least not without coercion. The danger of drifting from incentives to disincentives to outright compulsion is not some speculative fear, it is a historical fact, one that has been repeatedly demonstrated over the past century. Even now, those who campaign against reproductive rights use fears of low fertility to argue that women should not be allowed to terminate their pregnancies. And that is why anyone who cares about liberty should be very leery of government schemes to get people to have more babies.

You can find confirmation that economists cannot explain fertility by taking a good, long look at the scholarly literature on pro-natalist policies, which is filled with ad hoc explanations for particular cases and vain efforts to devise a more general theory. Bryan originally offered us one study from Quebec and implied that it showed that small bribes would get couples everywhere to have more babies. Why just this one study? Bryan writes that it was “the highest quality.” Now he cites another study from Austria and a small-scale literature review—presumably of lower quality—as if it proved the point. But there have been many dozens of studies of the impact of government policies on raising fertility, and several large-scale meta-analyses just over the last decade. Considering how crucial this point is for his entire argument, why not look at all the best peer-reviewed research, rather than just cherry-pick a handful that support the idea that we can buy babies on the cheap?

In 2003 a report by Joëlle Sleebos for the OECD looked at research from ten different countries, including eight separate studies from Canada alone. She still had to admit that it was merely a “partial review.” Nevertheless, she came to the following conclusion:

[M]ost studies seem to suggest a weak positive relation between reproductive behaviour and a variety of cash benefits and tax policies. Impacts of family-friendly policies are more contradictory, with several studies suggesting strong positive effects on fertility from higher child care availability but weaker or mixed effects from maternity and parental leave. More generally, however, these studies also suggest that no single “silver bullet” is likely to reverse recent declines in fertility rates in OECD countries.[1]

In 2007, a similarly ambitious analysis of the literature by Anne Gauthier came to much the same conclusion:

The analysis presented in this paper suggests that policies may indeed have an effect on families, but that the effect tends to be of a small magnitude and that it may possibly have an effect on the timing of fertility rather than on completed family size. In view of these results, the popularity of baby bonus schemes among governments, as a way of encouraging fertility, is difficult to understand. While the additional financial support is bound to be welcomed by parents, the overall effect on fertility is likely to be small.[2]

The most encouraging recent peer-reviewed meta-analysis, by John and Pat Caldwell together with Peter McDonald, confirmed that the consensus among researchers is that government expenditures to raise fertility “achieve little or nothing.” It conceded that this was likely true of industrialized democracies, but pointed hopefully to the example of countries behind the Iron Curtain. They appear to have helped stop fertility declines in the 1960s and ‘70s through “massive transfers,” including up to 10% of these communist governments’ budgets. Of course, the real standout was Romania, where Ceausescu imposed severe penalties for abortion, leading to a massive increase in the maternal mortality rate.

Bryan insists that the crimes of anti-natalism are far worse than those of pro-natalism, and describes them as a thing of the past—even though dozens of countries keep abortion unsafe and illegal. Personally, I would rather not tell a Romanian woman who suffered a septic abortion by a quack doctor that she is lucky compared to a Chinese woman who had a forced abortion overseen by Communist party cadres. I do not know how to compare the human cost of pressuring or compelling someone to bear multiple children against their will—and at risk to their health—to that endured by those who felt pressured or compelled to agree to use an unsafe contraceptive or endure assembly-line sterilization. That is why I insist that we must oppose coercive or manipulative population policies regardless of whether they aim to raise or lower fertility.

Fertility is not, after all, a good in and of itself, unlike liberty, prosperity, or good health. Fertility can be a curse for those who wish to avoid childbirth but are left to their own devices. As a society, we should protect the right of couples to decide whether and when to bear children not because we expect every one of them to make good choices. Rather, it is because we have learned that when the state is permitted to manipulate or coerce couples to decide one way or another, the consequences are much worse, and completely unpredictable. Before we join Bryan in bowing down before some new fertility cult, we should think harder about what—and who—we may end up sacrificing.

Notes

[1] Low Fertility Rates in OECD Countries: Facts and Policy Responses, OECD Social, Employment and Migration Working Papers, 15 (Paris: OECD, 2003).

[2] “The Impact of Family Policies on Fertility in Industrialized Countries: A Review of the Literature,” Population Policy Research Review 26 (2007): 339.

[3] “Policy responses to Low Fertility and Its Consequences: A Global Survey,” Journal of Population Research 19 (2002): 17-18.

1. I am pleased to see how muted Greg’s Malthusianism really is. His initial post suggested—at least to my ears—that bad times could be just around the corner:

So the downward march of food and energy prices since 1800 may well end soon. Current high prices may presage a food scarce-energy scarce future. If this causes the share of land and mineral rents in economies to again become significant, then we will have Malthus Redux.

But now he assures us that, “Income per capita will not fall in the future, even with continued population growth.” He continues:

So the issue here is not whether incomes will in the future decline because of population growth. That will not happen at current rates of technological advance. It is whether population growth comes to be a significant drag on future income growth.

Question: So would you accept a bet that the world’s economic growth rate for 2000-2050 will exceed the rate for 1950-2000?

2. I am pleased to in principle accept Greg’s proposed bet:

So if Bryan wants to bet even odds that farmland prices will be higher relative to average wages in 30 years time, I am happy to accommodate him. After all with the impending rise in world population to 9 billion people, surely given his views on population and innovation, one of these extra people will end forever the issue of land scarcity!

We just need to work out (a) whether this is a bet on U.S. farmland prices relative to U.S. average wages, or world farmland prices relative to world average wages; and (b) what we’ll consider the canonical measure of the price of farmland. For simplicity, I suggest we stick to the U.S., use the United States Department of Agriculture’s measure of the average value of farm real estate, and settle on January 1, 2041. $100 good for you, Greg?

3. Greg rejects Landsburg’s argument that population externalities are internal to the family:

The flaw in this argument is that the population externality, if it exists, is a reduction in wages for other members of a cohort which is not fully compensated by a rise in resource rents. That reduction falls almost entirely outside the family. Caplan’s kids are potentially reducing my kids’ earnings.

Since a half of families own no assets in most societies, population externalities would be sure to hurt them. So if there is a significant population negative externality there is no easy fix for your libertarian conscience through the Landsburg defense.

It is Greg’s argument that is flawed. Falling wages are a transfer from workers to employers (and indirectly, to consumers), not a negative externality. There is a distributional effect, nothing more.

4. On the positive effect of population on idea production, he writes:

The theoretical case for some positive effects of population on idea production seems compelling. The strength of this effect, and whether it is great enough to counteract the costs of population growth, is another matter.

Then adds:

But the empirical evidence population on idea production is weak, especially once we move to population sizes beyond those of remote island communities.

What would it take to convince you, Greg? The more populous periods of human history—most obviously the last few centuries—clearly produced more scientific, technological, and cultural innovations than earlier, less populous periods. More populous countries today produce many more scientific, technological, and cultural innovations that less populous countries. There’s even a +.46 correlation between population and gold medals in the 2004 Olympics—India notwithstanding. Here’s a challenge for you: Name the most credible measure of idea production that isn’t at least moderately positively correlated with population.

Here is Greg’s last question:

If population externalities were such a sure cure for stagnation, why no Industrial Revolution in China by 1 AD, or 1000 AD?

“Sure cure for stagnation”? No. Important cause of growth? Yes. And during this period, China was a major source of new ideas in the world; see Charles Murray’s Human Accomplishment. It wasn’t fast enough to bring an Industrial Revolution, but it was amazing in historical perspective. The real puzzle comes later, when China stagnates despite its high population. The mainstream solution to this puzzle, which I see little reason to doubt, is that the Chinese government forfeited its many advantages by deliberately suppressing innovation and communication with the outside world.

A reply to Matthew Connelly.

1. When I wrote Selfish Reasons to Have More Kids, I tried to review the whole literature on the effect of natalist incentives. But this wasn’t my focus, and based on Connelly’s references, I confess that I may have overlooked some relevant research.

Fortunately for me, as I pointed out in my target essay, the cost/benefit ratio of additional fertility is so favorable that we can drastically reduce our estimate of the benefits, drastically increase our estimate of the cost, and continue to enjoy a free fiscal lunch. This is an argument for tax cuts that almost all non-libertarians would find compelling. Can a libertarian really be less sympathetic?

2. Connelly writes:

Bryan insists that the crimes of anti-natalism are far worse than those of pro-natalism, and describes them as a thing of the past—even though dozens of countries keep abortion unsafe and illegal.

Did I say or even suggest that coercive natalism is a “thing of the past”? I don’t think I did. He continues:

I do not know how to compare the human cost of pressuring or compelling someone to bear multiple children against their will—and at risk to their health—to that endured by those who felt pressured or compelled to agree to use an unsafe contraceptive or endure assembly-line sterilization.

Question: Is this a general agnosticism about weighing one form of coercion against another? Or is it specific to the issue at hand?

3. I’m puzzled by Connelly’s claim that, “Fertility is not, after all, a good in and of itself, unlike liberty, prosperity, or good health.” It seems to me that, all else equal, it is very “good in and of itself” when one more person gets to enjoy the gift of life. Yes, you can point to downsides and trade-offs. But you can do the same for prosperity and health.

Matt, why are you so much more worried about “fertility cults” than “prosperity cults” or “health cults”? All can be rationales for oppressive policies. All have been. But as I said in my previous reply, libertarians have more convincing ways to defend liberty than flatly denying the goodness of these ends.

Bryan is gracious in admitting he may have underestimated what we might have to pay people to have more babies. So how much more would he be willing to pay? Given that his policy would only apply to taxpayers, might hedge fund managers with large families get a free pass? And would this not mean doubly penalizing working class couples unable to bear children? But my main concern is the unanticipated costs and risks—inevitable when we are fiddling with something that we do not really understand—including the opportunity costs of implementing such a plan when the country has far more pressing concerns than the fertility rate.

When I wrote that I did not know how to compare the crimes of anti-natalism to the crimes of pro-natalism, I was drawing a contrast with Bryan’s assertion that the former have swamped the latter. I should have asked how he made this judgment, especially now that I understand he recognizes that threats to reproductive rights are ongoing. People struggle to compare the great human rights atrocities of the 20th century, but at least we can count the bodies. How do we even begin to calculate the toll on women’s health and wellbeing of having to bear children against their will, and then compare it to the tragedy of others who were denied that right? Historians shy away from making these kinds of judgments since we believe it is hard enough simply to understand and explain, and real understanding is what we need most to avoid repeating the same errors.

Bryan and I must agree to disagree about whether fertility is a good in and of itself “all else equal.” Ceteris paribus can be a useful—though often misleading—assumption when positing causal relationships. But it is not helpful when we are trying to assess human values. Most people judge liberty, prosperity, and health to be good in and of themselves because they wish to live in a society that maximizes each one of them. Who wants to live in a society that maximizes fertility, especially if manipulating or pressuring couples to have more children comes at the cost of liberty, prosperity, and health? When it comes to fertility, other things have never been equal—especially not the costs and risks for men and women, rich and poor, the fit and the “unfit.”

Bryan objects to my intermediate position on future population growth. This is, will we return to subsistence income levels? No. Will there be significant net costs from population growth? Likely yes.

But I think it reflects a problem of his libertarian position on fertility that he has to have a world where there is NO negative population externality for his argument to go through. Will population growth create a Malthusian dystopia, as predicted in book after book by the likes of Lester Brown?[1]—most likely not.

But as world population continues to grow will we lose more animal and plant species? Yes. Will we have further global warming? Yes. Could there be, heavens forfend, an optimal level of world population below 100 trillion? Yes.

He objects that the fact that my extra child leads to a lower wage for your child is not an externality—it just reflects a redistribution of income. Just in the same way if I open up a coffee shop next to yours, I may reduce your income by taking some of your customers, but I have not created an externality.

But let us not get hung up on the murky definition of what is a true externality in economics. Let us just concentrate on the factual issue. If I have another child can that lead to a decline in the net income of people, counting all sources, outside my family? The answer to that is very much yes. As long as there are fixed resources, population increase depresses income per capita below what it would otherwise be. And that depression of income is felt not just by the children of the super fecund, but by a wide share of the population.

Before 1800 we see case after case where increased fertility or reduced disease, and the resulting population growth, cause substantial declines in living standards, even for those who themselves had modest fertility levels. All the descendants of the Bounty mutineers, for example, had to be evacuated from their tiny island home of Pitcairn in 1856, because the original population of 27 that landed and prospered in 1790 had risen in two generations to 193, at which level they could not feed themselves.

So Bryan needs population to have only positive effects on income per person. To this end he cites the fact that there is a positive association between medals per capita in Olympic sports and the population size of countries.[2]

Looking across countries is not a good test of population benefits, since there will be spillovers. Vatican City (population 500) gets to use laptops just like anyone else. But if Bryan wants to pursue this line, how would he account for Iceland?

Iceland has a population of 318,000, of whom 292,000 are native Icelanders. The native population speaks Icelandic, a language with a complex grammar similar to Old Norse. It has evolved little since the twelfth century. Icelandic is spoken by no one other than Icelanders.

300,000 people is a very small number of people. Equivalent sized cities in the US are Anchorage, Alaska and Stockton, California.

We would on Caplan’s theory of population expect this isolated community to have about as much prospect as the Tasmanians of pre-industrial Australia.

Yet Iceland has maintained a vibrant local culture and is a notable presence on the international scene. Start with the film industry. The 300,000 people of Iceland produced 70 films (features, documentaries etc) between 2000 and 2010, in Icelandic! I recently saw one, Jar City, which was very well done.

Iceland also has maintained a substantial literary tradition. Halldór Kiljan Laxness won the Nobel Prize for Literature in 1955. Arnaldur Indriðason is an internationally successful crime writer. In music also we have Björk..

The 300,000 people of Iceland are enough to sustain a respectable university. Iceland is host to an innovative project to map the DNA of hundreds of inhabitants from many different families (Decode Genetics). It is also the home of CCP Games, the company that developed the large and successful game EVE Online.

And of course, it was wildly innovative in its banking arrangements.

If population size is so crucial to innovation and economic activity, how come we hear so much about these obscure Icelanders? (And please don’t tell me it because of their good economic management!).

Notes

[1] For example, Saving the Planet: How to Shape an Environmentally Sustainable Global Economy (with Christopher Flavin & Sandra Postel) (1992), Who Will Feed China?: Wake-Up Call for a Small Planet (1995), World on the Edge: How to Prevent Environmental and Economic Collapse (2011).

[2] I do not know this study, but there are two things that make me skeptical.

First, some Olympic sports are team sports, where being from a bigger country would be an advantage. It may be the case that the fastest sprinter is equally likely to come from any person in the world, but if you are looking for the fastest 4 sprinters as in a relay team, then even per capita, Iceland will be at a disadvantage. So if done properly this study would have to be confined to individual events (it may have been).

Second, the huge disparities in country sizes mean that the slope of the regression line is essentially determined by a small group of very large countries. And there are enormous disparities in Olympic performance that are a function of government decisions on whether or not to pursue athletic success. China has quite deliberately chosen to sink huge resources into this.

Some responses to several excellent questions from Matt:

1. Matt’s concerned about the distributional effect of natalist tax credits:

Given that his policy would only apply to taxpayers, might hedge fund managers with large families get a free pass? And would this not mean doubly penalizing working class couples unable to bear children?

Actually, if the numbers I presented are remotely close to the truth, natalist tax credits would even benefit working class couples unable to bear children. My argument wasn’t merely that tax credits are a good idea all things considered. My claim, rather, is that natalist tax credits are a fiscal free lunch. Modest tax credits are enough to inspire the creation of new people who will pay far more in taxes than they’ll ever collect in services and benefits. You can question the estimates, but as I said, this free lunch is so big that you can drastically revise the numbers without changing this conclusion.

2. There is no easy answer to Matt’s toughest question:

People struggle to compare the great human rights atrocities of the 20th century, but at least we can count the bodies. How do we even begin to calculate the toll on women’s health and wellbeing of having to bear children against their will, and then compare it to the tragedy of others who were denied that right?

But I’ll try anyway:

First, it seems much more wrong to force a woman to have an abortion than to prevent her from having an abortion. I’m pro-choice, but I have to admit that the pro-life position is far from crazy. There’s at least a semi-plausible moral rationale for banning abortion. The arguments for forced abortion, in contrast, are so flimsy almost no one even bothers to make them.

Second, all else equal, coercing more people is worse than coercing fewer. And most women do not want and will not seek abortions whether or not they’re legal. But most women do want children; indeed, most want more than one.

3. Matt’s last point seems completely wrong to me:

Most people judge liberty, prosperity, and health to be good in and of themselves because they wish to live in a society that maximizes each one of them. Who wants to live in a society that maximizes fertility, especially if manipulating or pressuring couples to have more children comes at the cost of liberty, prosperity, and health?

Mathematically, as Henry Sidgwick pointed out, you can’t maximize more than one thing. And, although people may say they want to live in a society that maximizes liberty, prosperity, or health, no one would actually want to live in such a society. Why not? Because there are trade-offs. To maximize health, for example, you would have to force people to exercise and eat right—and keep ramping up the coercion until you reached the point where more coercion would actually start to hurt health. To maximize liberty, similarly, you would have to bite all the bizarre bullets that David Friedman offers in The Machinery of Freedom.

This doesn’t mean that liberty, prosperity, and health aren’t good in themselves. It just means that no one good thing should be “maximized.” Once you admit that, why not add population to the list of intrinsic goods? I’m glad to be alive. If one more person is born, he’ll probably be glad too.

In his last response, Greg Clark poses a few more challenges.

1. “Could there be, heavens forfend, an optimal level of world population below 100 trillion? Yes.”

I addressed this very point in my original essay:

One can admittedly imagine negative externalities of population vast enough to outweigh all the positives. Just picture a world so crowded that there’s no room to move. But there’s no sign that the real world is anywhere close. Over the observed range, people and good outcomes go hand in hand—and there’s no sign of anything else on the horizon.

2. Greg correctly states my position on the labor market externalities of population:

[Caplan] objects that the fact that my extra child leads to a lower wage for your child is not an externality—it just reflects a redistribution of income. Just in the same way if I open up a coffee shop next to yours, I may reduce your income by taking some of your customers, but I have not created an externality.

He objects:

But let us not get hung up on the murky definition of what is a true externality in economics. Let us just concentrate on the factual issue. If I have another child can that lead to a decline in the net income of people, counting all sources, outside my family? The answer to that is very much yes. As long as there are fixed resources, population increase depresses income per capita below what it would otherwise be. And that depression of income is felt not just by the children of the super fecund, but by a wide share of the population.

As long as the transmission mechanism is “labor supply goes up, so wages go down,” Greg’s story remains a mixture of truism and error. Suppose a fixed supply of land is the only non-labor asset. If I have a million kids, pushing wages down by $1 per hour, each of my kids will have lower wages and very little land. As a result of my high birth rate, all other net sellers of labor will earn $1 per hour lower wages and have the same amount of land. And all other net buyers of labor will pay $1 per hour lower wages and have the same amount of land. Net effect on wages outside my family: zero. The only reason per-capita income falls is that my million kids own so little land.

If you consider this scenario further, it turns out that per-capita income outside my family will actually rise. My million land-poor kids will also bid up land rents—a net transfer from my descendents to landowners. There are naturally distributional effects: renters are worse off, land owners are better off. But the net effect of my fertility on per-capita income outside my family is clearly positive.

3. I agree with Greg when he says, “Looking across countries is not a good test of population benefits, since there will be spillovers.” But these spillovers cause us to understate the benefits of population! In a global economy, each country’s contribution to innovation depends on (a) the country’s supply of innovation, and (b) the world’s demand for innovation.

4. Greg wants to know how I would account for Iceland. The obvious answer is that Iceland is an extreme outlier. My challenge for Greg was, “Name the most credible measure of idea production that isn’t at least moderately positively correlated with population” – not “Name a single counter-example.”

Greg says that Iceland’s 318,000 inhabitants produced 70 films between 2000 and 2010. It’s great to be such an over-achiever. But what about the overall correlation between annual movie production and population? Using IMDB’s numbers for 2003’s top fifty film-producing countries, I calculate movie-population correlation of +.67. If you drop underperforming mainland China from the sample, the correlation jumps to +.88. (Raw numbers here, Microsoft Excel sheet.)

I have to reiterate my challenge for Greg: Name the most credible measure of idea production that isn’t at least moderately positively correlated with population.

5. One last question for Greg: Do you accept the terms of my bet on land prices in 2041?