A better interpretation of crime statistics for Chicago suburbs

The Daily Herald looks at recent crime figures in Chicago area suburbs. How should we interpret such numbers?

Violent crimes increased last year in half of 80 suburbs, says a new report by the FBI we’ve been analyzing.

Property crimes increased in more than 40 percent of the suburbs.

The Uniform Crime Reporting Program’s 2015 report shows Rosemont had a 94 percent increase in violent crimes, from 18 in 2014 to 35 in 2015. Most are assaults, but the category also includes rape, homicide and robbery. The village had a 29 percent increase in property crimes, which include arson, burglary and vehicle theft.

Other more populous suburbs had larger numbers of violent crimes in 2015, including 650 in Aurora, 261 in Elgin and 128 in Naperville.

Violent crimes remained largely flat in Palatine, with 36; Des Plaines, with 50; and Arlington Heights, with 42; while some communities saw crimes decrease across the board. Buffalo Grove saw an 80 percent decrease in violent crimes, to 2, and an 18 percent decrease in property crimes, to 234, while Prospect Heights saw a 33 percent decrease in violent crimes, to 14, and a 29 percent decrease in property crimes, to 112.

What I would take away:

  1. Looking across communities, there was not much change as half of the suburbs did not experience a rise in violent crimes and property crimes increased in less than half of the suburbs.
  2. It is interesting to note larger jumps in crime in certain communities. However, these should be interpreted in light of #1 and it would be more helpful to look at crime rates in these larger suburbs rather than just relying on occurrences.
  3. The last paragraph notes some major changes in other suburbs. But, some of these suburbs are smaller and a large decrease (80% in Buffalo Groves means a drop from 10 to 2) or increase could be more a function of not many crimes overall rather than indicate a larger trend.
  4. There is little indication of crime figures or rates over time which would help put the 2015 figure in better perspective.

All together, the headline “40 suburbs see spike in violent crimes in 2015” is not the most accurate. It may catch the attention of readers but neither the headline or article sufficiently discuss the statistics.

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