Okay, I’m looking around a little. The arrest rate is 810.5 per 100,000 inhabitants. That’s quite a bit lower than your rate. Why is that?
PDF File: http://www.isp.state.il.us/docs/cii/cii05/execsummary05.pdf
This seems to be germane: Survey of State Criminal History Information Systems, 2003 from the Bureau of Justice Statistics. Table 2 (in the pdf file) shows 1.5 million individuals in the “state criminal history file” in Michigan in 2003; the adult population is about 7.5 million, for a 20% rate. For Illinois, 4.2 million individuals are in the “state criminal history file”, with an adult population of 9.3 million, for a 45% rate.
Forty-five percent seems awfully high to me (and I can’t believe Illinois is that much more criminally-minded than Michigan), so I suspect there’s a difference in the definition of “criminal history file.” In any case, I’m not sure exactly how these numbers are arrived at, but the percentages bracket wring’s 28%.
I had no idea our populations were that close in number. That’s rather surprising. I can’t believe those numbers, either.