Previous posts in this series have examined the latest available incarceration data from Indiana, Minnesota, and Wisconsin. This post considers historical data. I’m particularly interested in the impact of a major change in sentencing law that was adopted in Wisconsin in 1998. Under the “truth in sentencing” law, parole was abolished for crimes committed on or after December 31, 1999. What impact did this have on the size of the state’s prison population? Two hypotheses occur to me. First, if judges continued to impose the same nominal sentences that they had been imposing, one would expect the prison population to grow because offenders would be serving longer real sentences. Alternatively, judges might have reduced their nominal sentences to account for the loss of parole release options, attempting thereby to achieve the same real sentences as before TIS; such discounting would presumably lead to stability in the imprisonment rate.

The data, set forth in the table below, seem to support the latter hypothesis, with the current rate of imprisonment almost exactly matching that of 2000, the first full year after TIS took effect. Indeed, since 1999, the state’s imprisonment rate has been remarkably stable. The single largest annual change since 1999 was a 5.8% drop in 2005. This makes for quite a contrast with the volatile 1992-1999 time period, when annual increases averaged 12%.

The picture becomes even more interesting if we focus on Wisconsin’s imprisonment rate relative to that of peer states Indiana and Minnesota.

In the first post in this series, I explored the large gap between the incarceration rates of Minnesota and Wisconsin. In the second, I discussed racial disparities in the incarcerated populations of the two states. The disparities in both states are wide, although Wisconsin’s are somewhat larger. In this entry, I add a third state, Indiana, to the statistical comparisons. As another medium-sized midwestern state, one might expect that Indiana would have criminal-justice numbers that are similar to Minnesota’s and Wisconsin’s. Indiana’s numbers, however, point to a criminal-justice sustem that is much larger and harsher than those of its northern neighbors.

As detailed in the table that appears after the jump, Indiana’s imprisonment rate (about 460 per 100,000) easily outstrips Wisconsin’s (387) and dwarfs Minnesota’s (178). Perhaps even more surprisingly, Indiana’s probation population also exceeds Minnesota’s. My Minnesota-Wisconsin comparison suggested that Wisconsin imprisons many defendants who would get probation in Minnesota, leading to a much smaller probation population in the former than the latter. But Indiana seems to incarcerate the same way that Wisconsin does, without any accompanying reduction in the probation numbers.

For that reason, Indiana’s total supervised population of 167,872 is the largest of the three states (although Minnesota, with the smallest overall population of three, still has a somewhat larger per capita supervised population, thanks to its enormous per capita probation number).

Indiana also leads the way in crime.