Over the years I’ve written about the work of Bruce Western, Becky Pettit, Chris Uggen, and other scholars who study mass incarceration in the United States. By now, the basic outlines of the phenomenon are pretty well established and, I hope, widely known. Two features stand out: its sheer scale, and its disproportionate concentration amongst young, unskilled black men. It should be astonishing to say that more than one percent of all American adults are incarcerated, and that this rate is without equal in the country’s history and without peer internationally. Similarly, it may seem hard to believe that “five percent of white men and 28 percent of black men born between 1975 and 1979 spent at least a year in prison before reaching age thirty five”, or that “28 percent of white and 68 percent of black high-school dropouts had spent at least a year in prison by 2009”.

Those numbers come from the first chapter of Becky Pettit’s new book, Invisible Men: Mass Incarceration and the Myth of Black Progress. You can read the first chapter for free, but I recommend you buy the book. Pettit’s argument is that mass incarceration is such a large and intensive phenomenon that it distorts our understanding of many other social processes.

Pettit and others have been arguing for a long time that incarceration is by now a modal event in the life-course for young black men. Black men are more likely to go prison than complete college or serve in the military, and black, male, high-school dropouts are more likely to spend a year in prison than to get married. These social-structural changes have consequences for measuring and counting those involved. The incarcerated population is hard to count properly, and in many commonly-used data sources, like the Current Population Survey, its size and composition is poorly estimated or simply excluded. This has knock-on effects for our understanding of trends—especially changes in racial gaps—in things like rates of educational attainment, the employment-to-population ratio, group differences in average earnings, and voter turnout. In many of these cases, Pettit shows, what look like improvements over time are partly or mostly explained by miscounting due to the incarcerated population. This invisibility can happen both while people are in prison (as many surveys don’t adequately count the prison population) but also on release, where the marginal status of many ex-convicts makes them hard to reach in surveys built around sampling individuals stably attached to single households.

So, for example, Pettit shows that

Reliance on data from the Current Population Survey might lead one to believe that the high school dropout rate has fallen precipitously and that racial inequality has narrowed during the period of penal expansion … [CPS data] imply that the black-white gap in high-school completion, through either formal schooling or a GED, narrowed from 13.6 to 6.3 percentage poitns between 1980 amd 2008. Including inmates, we find little improvement in the black-white gap in high school for the last twenty years … including inmates suggests that the racial gap in high school completion among men has hovered close to its current level of 11 percentage points for most of the past twenty years" (55, 60).

Much the same seems to be true of group-level estimates of employment rates, wages, and voter turnout. Pettit argues in passing that the strong turn in the social science literature towards estimating causal effects (between education and wages, say) has led to a lack of attention to the quality of the purely descriptive numbers, and to a tendency to ignore the “acute sample bias associated with the exclusion of socially marginal groups from sample surveys” (107). This neglect feeds forward into that research, however, even if the research is not about inmates or criminal records at all, as it tends to bias estimates of the effects of, say, education on earnings. Moreover, Pettit argues,

… incarceration is so common in some sociodemographic groups that there are few comparable individuals in the population who have not experienced incarceration. The ubiquity of incarceration among low-skill black men undercuts research designs that require comparison groups to isolate the effects of incarceration from other factors like race, low education, or living in disadvantaged neighborhoods. A significant body of causally oriented research uses quasi-experimental designs … that compare the outomes of inmates or former inmates with similarly-situated indviduals who have not been to prison or jail. There is no valid comparison group for many of America’s inmates exactly because incarceration now inheres in whole sociodemographic groups ..

A broader theme of the book is that inmates and ex-inmates are at once constantly under surveillance and effectively unseen. Crime coverage is ubiquitous even as crime rates have been falling for years. The incarcerated and formerly-incarcerated population is enormous, but its real presence is invisible in many standard sources of data about the American population. The downstream consequences for our basic picture of what America is like and how it has been changing are underappreciated. In an era where “Big Data” is already an overused buzzword, Pettit’s book is a sobering reminder of the consequences of having a numerically large, socially consequential, but often statistically invisible population.