The scale of imprisonment in the United States: twentieth century patterns and twenty-first century prospects.

• Author: Zimring, Franklin E.
• Position: Centennial Symposium: A Century of Criminal Justice

1. INTRODUCTION

   The prison has been far more important to criminal justice practice than to academic theory in the century examined by this Symposium. Imprisonment is the dominant severe criminal sanction worldwide and there is no evidence that its hegemony at the deep end of crime control will change. But the study of imprisonment has not been a major feature of criminal law theory at any time, while some aspects of prisons have commanded attention in the literature of criminology. So imprisonment has played a dominant role in American criminal justice but a minor role in the discourse about criminal law. The Harvard Law Review, for example, listed twenty-seven articles with "prison" or "imprisonment" in the title in one hundred years of publication beginning in 1910.

   The interdisciplinary character of the Journal of Criminal Law and Criminology and its crime focus made it into the leading forum in law-related scholarship covering issues of prison operation and function. No fewer than 155 main articles were published with "prisons" or "imprisonment" in their titles in a century of publications, by far the largest concentration one would find in any scholarly journal closely linked to legal education. (1) And prisons played a prominent part in the scholarly portfolio of the Journal from the very beginning, with slightly more articles on prisons in the first half of its volumes than in the second. The range of prison-related topics covered from the beginning--including comparative and empirical work--was impressive.

   But little of the first half-century of the Journal touched on the central issue in this analysis--what I shall call the scale of imprisonment. Zimring and Hawkins define the issue of scale as analysis of the appropriate "size of a society's prison enterprise in relation to other criminal sanctions and to the general population. How many prisoners? How many prisons? What criteria should govern decisions about how large a prison enterprise should be constructed and maintained?" (2)

   Only one of the more than seventy articles with prison in its title that appeared in the Journal in its first half-century was principally concerned with rates of imprisonment: an article by Edwin Sutherland describing the decline in rates of imprisonment in England. (3) One important reason for the lack of scholarly attention to variation in the rate of imprisonment in the United States is that there was not a great deal of variation over time in the rate of imprisonment.

   Indeed, the lack of dramatic variation in rates of imprisonment inspired Alfred Blumstein and Jacqueline Cohen to construct what they called "A Theory of the Stability of Punishment" (4) in the Journal in 1973, probably the most important and certainly the most ironically timed article on imprisonment in the Journal's first century. Blumstein and Cohen posit that levels of severe criminal punishment trend toward stability over time and they offered as evidence of this phenomenon the rather stable rates of imprisonment in the national aggregate over the years 1930-1970. Their Figure 2 is reproduced from Blumstein and Cohen as my Figure 1. The interpretation of this data was straightforward:

   It can be seen from Figure 2 that over that period the imprisonment rate was reasonably constant, having an average value of 110.2 prisoners per 100,000 population and a standard deviation during that time ... of 8.9 prisoners per 100,000 population.... The stability of the time series is especially noteworthy when it is considered that the population of the United States increased by over 50 percent in the same period. (6) [FIGURE 1 OMITTED]

   Twice more in the 1970s, Blumstein and his associates would produce data and analysis to augment their stability of punishment theory, (7) but then their entire theoretical structure was overtaken by events. From its low point in 1972, U.S. prison populations had begun a consistent and unprecedented climb. Figure 2, taken from U.S. Bureau of Justice Statistics data, shows an uninterrupted increase in aggregate imprisonment rates that lasted the full generation after 1972.

   [FIGURE 2 OMITTED]

   The contrast between the four decades after 1930 and the three and a half decades after 1972 is stark. The highest annual imprisonment rate in the 1930-1970 period was 38% above the lowest (131.5 versus 95.5 per 100,000) and there was no clear trend over time. In the thirty years after 1972, the rate of imprisonment grew every year and the rate of imprisonment by 2007 was five times greater than at the beginning.

   The first impact on scholarship of this unprecedented increase in the use of prisons in the United States was to end any serious discussion of "stability of punishment." That theory was produced by flat trends over time in the United States after 1925 and was destroyed by the imprisonment boom that followed 1972.

   The second product of the sharp increase in American prison population was academic interest in what features of society and government might influence rates of imprisonment over time. Once the dynamic and non-homeostatic qualities of imprisonment rates were established by the history of imprisonment after 1975, the causes of variation in imprisonment over time and cross-sectionally became an important topic for empirical analysis. The same upward march in prison population that ended interest in stability of punishment generated curiosity about the scale of imprisonment as a variable in crime policy and governance.

   There are two parallels between the "stability of punishment" exercises of the 1970s and the more recent efforts to comprehend and measure what determines the scale of imprisonment in the United States. The first important shared characteristic of these two lines of inquiry is that each theory was derived from and driven by empirical data. For all its Durkheimian analysis, the inspiration for Blumstein and Cohen's stability of punishment insight was the flat distribution of imprisonment rates over time in the United States, a pattern that invited speculation about its potential causes. In that sense, the stability pattern was a practice in search of a theory before any explanation was produced. The more recent work on the scale of imprisonment was also provoked by the changing trends that demanded explanation and analysis. All of the recent studies of imprisonment scale have been inspired by these sharp increases, so here again the data to be explained arrive prior to the theories to be tested.

   The second parallel is an unjustified assumption of temporal normality. Despite the fact that theories of stability and then of variability were inspired by provocative empirical trends, the analysis of historical data testing these theories has assumed that the periods to be analyzed are normal and typical. In the earlier work, the observed stability was assumed to be representative of other periods as well, so that the generality of patterns observed could be expected. Again, in the statistical explanations of the period after 1972, the empirical analysis has been assuming that the prison trends of the thirty years after 1972 are representative of other periods and public moods so that the statistical relationship and magnitude of effects noted in this period will hold for other times and conditions.

   This Article focuses on three aspects of the prison trends in the United States since 1975. First, I discuss the size and generality of the increase in prison population with special emphasis on the features of government that make the pattern of growth so surprising. Second, I identify and discuss two central empirical questions about the imprisonment boom after 1972. Part IV explores the effects of the analysis in Part III on the proper method of testing whether crime rates are important in predicting imprisonment. The final section of this Article asks whether and to what extent the volatility in the growth of prison populations might also signal that major drops in the scale of imprisonment might happen soon.

2. THE MAGNITUDE OF PRISON GROWTH

   The thirty-five years after 1972 produced a growth in rates of imprisonment that has never been recorded in the history of developed nations. Figure 3 compares the rate of imprisonment in 1972 with the rate in 2007.

   The 502 per 100,000 rate of state and federal imprisonment is not only five times the rate of imprisonment in the base year of 1972 but also almost four times the highest level of imprisonment in the four decades prior to 1970. By the early 1980s, the U.S. prison population passed its previous high rate and continued a sharp increase without any pause for more than two additional decades. In the generation after 1970, the rate of imprisonment in the United States doubled (between 1972 and 1988) and then doubled again.

   When this growth began in the 1970s, the rate of imprisonment in the United States was on the high end of western democracies but not what statisticians would call an "outlier" totally apart from the other nations in the G7. (9) But the rate of imprisonment achieved by 2007 in the United States was three times that of any fully...