I stand corrected

I think I will eat my crow before someone dishes it up for me. I shot from the hip--or maybe from the lip. In my previous post I claimed that relative police reporting practices are responsible for the disparity in traffic crash rates between Lincoln and Omaha. In fact, this appears not to be the case. I stand corrected.

Despite differences in our reporting practices (which may still exist), the difference between our crash rates described in the Omaha World Herald article do not appear to be due to the numerator (number of crashes), but rather the denominator: million miles driven. I went to the actual source data, the monthly recapitulations of traffic crash reports from the official keeper-of-the-records: the Nebraska Department of Roads. Here's what the "winter" of 2007-2008 looks like, when you examine box 17 on these monthly reports:

It appears from these data that the crash rates per capita in these cities are very similar. I did the same math for calendar year 2007 and for 2008, with similar results: Lincoln's rate per capita is within a gnat's eyelash of Omaha's: very slightly greater in 2007, very slightly lower in 2008. This would tend to confirm Allstate's ranking of traffic crash claim rates, which put us very close together.

Since the number of crashes lines up with population, the difference in crash rates per million miles driven is attributable to the much greater miles driven in Omaha--way out of proportion to any population difference. One might reasonably conclude that drivers in a larger city drive a little further on average, but that effect should be pretty minuscule. I suspect that the theory floated by Fred Zwonechek of the Nebraska Department of Motor Vehicles concerning the influence of a interstate travel through Omaha upon the million-miles-driven denominator is correct.

In the future, Casady, do your analysis before popping off. Mea culpa.