In the previous post in this series, I took the imprisonment data from Indiana, Minnesota, and Wisconsin back to 1991.  I’ve been interested, though, in pinpointing when exactly the Minnesota-Wisconsin imprisonment disparity arose, which requires going back further — much further, to the 1950′s.  Here are the numbers:

The numbers tell a remarkable story.  Here are some of the parts of that story that stand out for me:  

First, imprisonment rates in all three states were much lower in 1950 than they are today.  Of the three, Minnesota’s imprisonment rate grew the least between 1950 and 2010, and its rate nearly tripled.  Wisconsin, with the most dramatic increase, saw its imprisonment rate more than sextuple.

Second, the increases from 1950 to 2010 did not follow a smooth path.  Rather, 1975 was a radical breaking point in all three states.  Between 1950 and 1975, imprisonment rates fell quite markedly in Indiana (down 39.4%) and Minnesota (33.3%).  True, Wisconsin’s rate increased in that same time period, but by only 10.7% — a very modest increase over a twenty-five-year period, at least relative to what was about to happen.

Then, in the late 1970′s, everything changed.  In the seven five-year intervals between 1975 and 2010, the three states were routinely experiencing imprisonment-rate increases of 20% or more.  Before 1975, the single largest burst of imprisonment had been Indiana’s 12.9% increase between 1955 and 1960, which was swiftly followed by a 21.7% decrease in the early 1960′s.  By contrast, the largest burst after 1975 was Wisconsin’s whopping 77% increase between 1995 and 2000 — which was followed by yet another (albeit far more modest) increase between 2000 and 2005.

Before 1975, states were up some years and down others.  Since 1975, the trend has been pretty much exclusively in one direction: up.

Overall, since 1975,  Indiana is up 530%; Minnesota, 323%; and Wisconsin, 496%.

Third, while Indiana and Minnesota have retained the same position relative to one another through the whole time period, Wisconsin has shifted from being least harsh of the three to most harsh to now being in the middle.  In 1950, Wisconsin had the lowest imprisonment rate, but swiftly lost this distinction to Minnesota.  The change was not so much because of a big jump in Wisconsin, but because Wisconsin’s rate remained relatively flat while Minnesota and Indiana were experiencing dramatic decreases.   Then, Wisconsin’s imprisonment rate surpassed even Indiana’s due to that extraordinary 77% increase in the late 1990′s.  Since 2000, however, Wisconsin has moved back to second place as its imprisonment rate has returned to the sort of stability we saw in the 1950-1975 time period.  Minnesota and Indiana, by contrast, have remained more in growth mode since 2000.

So why is Wisconsin out of sync with its sister Midwestern states: modest growth in imprisonment from 1950 to 1975, while the other states were experiencing substantial drops; the most dramatic rate of growth of the three between 1975 and 2000; and then a leveling off since 2000, as the other states have continued to grow?

On the other hand, there is another way in which Indiana and Minnesota look very different from one another: volatility.  Although Indiana and Minnesota have consistently moved in the same direction, Indiana tends to move to a much greater degree, whether up or down.  Thus, the average percentage change over the thirteen five-year periods in Indiana has been 23%, while Minnesota’s average is only 16%.  I wonder if this says something about a greater overall stability in the legal or political systems in Minnesota than in Indiana — on the face of it, Minnesota’s systems seem better able to absorb whatever external pressures there are for abrupt change in the criminal-justice system.  From a planning and administration standpoint, Indiana’s volatility would seem quite problematic relative to Minnesota’s stability.

The Wisconsin volatility story is truly odd: Wisconsin was actually the most volatile of the three states between 1975 and 2000, but has otherwise been the most stable.  What happened between 1975 and 2000 that so badly undermined whatever shock absorbers we have that normally keep the criminal-justice system on an even keel?  (Pardon the mixed metaphor.)  And was there anything about the Truth in Sentencing law that helped finally to right the ship in 2000?

Finally, let’s consider the origin of the Minnesota-Wisconsin disparity.  In 1955, the two states had the same imprisonment rate.  This suggests that the current wide disparity is not an inevitable product of deep-seated differences in state culture, but results from contingent policy choices and/or some other set of  social forces that have operated differently in the two states over a limited time period.

Here are the disparity figures:

For the most part, the story is one of a slow, steady increase in the Wisconsin-Minnesota divide.  For this reason, it seems unlikely that any one particular policy choice (e.g., Minnesota’s adoption of a widely admired sentencing guidelines system in the 1980′s) deserves the credit or the blame for a lion’s share of the present-day disparity.

Two particular periods of time seem particularly interesting to me and worthy of further investigation.  One is the 1950′s, when Wisconsin’s imprisonment rate jumped nearly 20% as Minnesota’s was falling.  This was the time period that set the two states on a long-term path to disparity.

The other is the 1990′s, when the two states initially experienced about equal rates of growth, but then Wisconsin’s exploded while Minnesota’s dropped.  As a result, the disparity between the two states jumped more dramatically between 1995 and 2000 than in any other five-year period.  It is hard not to have the sense that something went horribly wrong in Wisconsin’s criminal-justice system in the late 1990′s — something that Minnesota, which had seemed to be on the same track as Wisconsin in the early 1990′s, managed to avoid.

The next post in this series will take the crime and race data back to 1950.

Cross posted at Life Sentences.