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.
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.