Why do nations jail? It’s a rich man’s folly, says Jan van Dijk from Tilburg University in the Netherlands. He demonstrates this with a neat graph, which shows a straight line between the imprisonment rates in relation to homicides and the GDP of a large global sample of countries: The richer countries are, the more they use imprisonment when meting out punishment to citizens. Similar results are obtained by researchers who use the United Nations Human Development Index: the more developed nations, which also have a higher GDP, have higher imprisonment rates than poor and less developed countries. Jan van Dijk has a point even from a historical perspective; prison became the dominant tool of crime control in the nineteenth century when European states became more affluent and could count on a steady stream of (tax) income. Obviously, imprisonment is a tool of criminal justice not affordable to all and sundry.
In most global comparisons of imprisonment the United States is a visible outlier. It not only stands out among its peers, the rich and developed countries, with its “historically unprecedented and internationally unique” experiment in mass incarceration housing 25% of the world’s prisoners. Imprisonment in the United States also by far exceeds imprisonment in the poorest and cruellest dictatorships in the world, even if we concede that these have other ways of dealing with citizens and their crimes and provided their data are credible. The unprecedented growth and unparalleled size of the U.S. prison population between 1970s and the first decade of the 21st century attracted an enormous amount of attention among criminologists. Was this just another case of American exceptionalism, or was the United States in the vanguard of a development that would become infectious globally? Most criminologists bought into the latter perspective. As a “hegemonic punitive worldview” took hold of them they saw “no escape from a punitive future,” neither for the United States nor elsewhere. 
This was the start of the search for the one magic-bullet variable that could explain why nations generally jail, and why the United States does so extraordinarily and massively. The emerging candidate was broadly labelled “neo-liberalism.” Neo-liberalism’s manifestations of deregulating the economy and downsizing the welfare state were at the core of most accounts of penal systems and the punitive turn across the globe, in the United States, Latin America, Australia, New Zealand, and Europe with the widely accepted argument that “the rich get richer and the poor get prison.” Another master narrative was based on the observation that nations with majority rules in their electoral processes have higher imprisonment rates. In both cases, the empirical foundations were shaky: a small number of highly selective country cases were used, imprisonment rates differed much less than the theory would have required, and evidence to the contrary was ignored, as e.g. the fact that neither Reagan as governor of California or Margaret Thatcher as Prime Minister of the United Kingdom had overseen increases in imprisonment during their time in office.
And the search goes on. Do civil law systems have in-built restraints, as Daniel D’Amico proposes? A global sample would include a large group of well-off European countries and another group of developing Latin American countries both with low imprisonment rates but for very different reasons. The European countries in particular stand out with a regional regime of oversight and care for prisoners, which considerably increases costs per prisoner, and in most of them prisoners have the right to vote (notable exceptions are the United Kingdom and a few post-Soviet states). It is however worthwhile to have a close-up on civil law systems. They have indeed in-built restraints and moderating elements which insulate and distance criminal justice from direct democratic accountability and community pressure that has ratcheted up U.S. imprisonment rates. American criminologist Frank Zimring argues that such “professionalization of punishment” combines several “leniency vectors” that keep imprisonment low. It is a defining feature of civil law systems that decisions are made by professionals and according to professional standards, and criminal justice officials are not directly elected. In contrast, communities and the electorate seem to have been a driving force behind skyrocketing imprisonment in the United States. During the past decades they were in ardent opposition to “big government” criminal policies that were seen as ignoring community demands and demonstrating undue sympathy for and “inappropriate leniency” toward the offender.  Voters in California supported criminal justice policies that lay the ground for ever increasing imprisonment in that state; they finally turned around in 2012, when they prudently decided that they would not spend a tax increase on ever more prisons and prisoners. D’Amico’s own findings definitely rule out the local level as a panacea against high imprisonment rates.
Criminologists have long known that factors that work when comparing countries, communities, and neighbourhoods do not explain changes over time. Thus the factors that explain why nations jail might fail when it comes to explaining the “hockey stick” shaped trend of U.S. mass imprisonment. The year 2009 provides a reality check for all theorizing on mass imprisonment in the United States: It was the year when imprisonment growth in the United States came to a halt, and when the numbers started to decrease after nearly four decades of relentless growth, a downward trend that has not stopped up to date. California led the U-turn way with more than 4,000 prisoners less, and half of the states have followed suit. As a robust signal of an end to the trend of mass imprisonment, prisons were closed in California, Nebraska, and New York. In 2012 28,500 prison places were either closed or under consideration for closing with estimated savings of nearly $340 million in the first year alone.
2009 was the year after the financial crisis, and this is no coincidence. The 2008 financial crisis was related to a severe fiscal crisis which was recognized in California and other states long before; New York repealed legislation that had extended prison sentences across a range of offences and offenders as early as 2003. Fiscal and cost arguments played an important role in these changes and continue to do so. It comes as a surprise for many criminologists that the same neo-liberals and fiscal hawks who had been blamed for “mass imprisonment” were now in the driving seat for penal reform. Prominent Republican Newt Gingrich now saw an “urgent need to address the astronomical growth in the prison population, with its huge costs in dollars and lost human potential,” and concluded that “conservatives must lead the way to fix it.” “Right on Crime,” a conservative think tank, explains the turn in conservative penal policies: “How is it ‘conservative’ to spend vast amounts of taxpayer money on a strategy without asking whether it is providing taxpayers with the best public safety return on their investment?” “[Conservatives] have changed their minds about what prison means. Prisons increasingly stand for big government waste …”. 
Elizabeth K. Brown tested two sets of factors that were associated with states’ legal reforms that reduced “reliance on incarceration”: budget pressures and the presence of Republicans in the state legislature and the governor’s office. Budget pressures increased the inclination of the state legislature to pass such legal reforms. In contrast, the amount of Republican seats reduced the efforts and success of such reforms. As it turns out bipartisanship is decisive: As neither of the two parties wants to be seen as “soft on crime,” there is a huge incentive for bipartisan agreement, which is furthered by a strong presence of Democrats in state legislatures. Change is initiated and gains momentum from “what strong, ideologically defined partisan activists and politicians come to believe is their own, authentically conservative or liberal position.” Information on the failure of mass imprisonment besides its tremendous costs is not seen as threat but rather as a confirmation of political and faith-based identities and beliefs. When conservative activists and politicians enter unexpected alliances, and readjust their positions, and when bipartisan politics are increasingly important, it is time for criminologists to re-think their theories of U.S. mass imprisonment.
If two trends look like hockey sticks there might be some common ground which kicks them off. Economist Deirdre McCloskey identifies the values of human dignity and liberty, and the revaluation of the status of the middle classes, as decisive drivers of the unprecedented growth of GDP across the globe. My own research shows that values like liberal individualism and egalitarianism are not related to how many are sent to prison, but significantly to the treatment of prisoners. Both might be nonetheless related: more care for the dignity and liberty of those who failed might make nations more cautious in the use of imprisonment, not the least because it increases the costs of imprisonment. In June 2015 a group of criminal justice practitioners, politicians, and criminologists, including a democratic governor and chief prosecutor from the United States visited Germany to see “how Germany does prison”. What they brought home was the need to “fundamentally rethink values” with an emphasis on the protection of and respect for the human dignity of prisoners, which not only is part of the German Basic (Constitutional) Rights, but also animates the Eighth Amendment of the U.S. Constitution that bans cruel and unusual punishment. A discourse on human dignity and “second chances” for prisoners has started across the political spectrum; these represent fundamental American values, which need to be regained in criminal justice, and thus lead a revaluation of its citizens in prison. Many European countries, including Germany, have considerably lower recidivism rates then the United States. Spending on prisoners rather than on warehousing them seems a better way to deliver the goods.
Among the delegates was a district attorney whose father had narrowly escaped death in the Bergen-Belsen concentration camp as a five-year-old. Seeing German prisons in 2015 he was confident that “countries can change.” Let us not forget that it was the United States that set post-war Germany on this trajectory of change. The people of the United States and their politicians have an amazing and unparalleled capacity for change; half a century for the road from segregated buses to an African-American in the White House is a short time span. I am confident that in 50 years’ time mass imprisonment in the United States will be a distant memory.
 S. Listwan, et al 2008. “Cracks in the Penal Harm Movement: Evidence from the Field” Criminology and Public Policy 7: 423-465, at 423
 M. Cavadino, J. Dignan 2006: Penal Systems. A Comparative Approach. London: Sage; J. Reiman 2000. The Rich Get Richer and the Poor Get Prison. Oxford, New York: Routledge
 F. Zimring, D. Johnson 2006. “Public Opinion and the Governance of Punishment in Democratic Political Systems.” Annals of the American Academy of Social and Political Science, 605: 266 – 280, at 274
 F. Zimring, G. Hawkins, S. Kamin 2001. Punishment and Democracy: Three strikes and you are out in California. Oxford: OUP, 231
 V. Barker 2009. The Politics of Imprisonment. Oxford, New York: OUP
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 N. Porter 2012. On the Chopping Block 2012: State Prison Closings. The Sentencing Project, Washington DC
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 The US is not included in the data on prison conditions as these are collected by the US State Department; S. Karstedt 2011. “Liberty, Equality and Justice: Democratic Culture and Punishment.” A. Crawford (ed.): International and Comparative Criminal Justice and Urban Governance: Convergence and Divergence in Global, National and Local Settings. 356-385.
 N. Turner, J. Travis 2015. “What we learned from German Prisons.” The New York Times, 7 August 2015 . http://www.nytimes.com/2015/08/07/opinion/what-we-learned-from-german-pr… (31.8.2015)
 M. Chammah 2015. “How Germany does prison”. https://www.themarshallproject.org.2015/06/16/how-germany-does-prison. (31.8.2015)