Tuesday, June 11, 2013

AH, STATISTICS: Within Official Police Boundaries, Robberies Hit Historic Highs

Earlier this evening, we posted our resident data driller's breakout of how reported robberies have increased by 54% in Wrigleyville and Boystown since 2001, while the city's overall robbery rate dropped 27%.

But we had another question for him to work on. How have robberies performed within the Chicago Police Department's official police "beats" that cover Wrigleyville and Boystown?

The current Wrigleyville and Boystown police  "beats." (Image: Chicago Police Department)

It'd be easy to just get this data from the city, if they hadn't merged the 19th and 23rd districts last year and then redrawn the beat borders. But the city did do that, so our nerd had to work a little bit.

Here's the truth:
• From 2001 to 2012, the city's reported robbery rate decreased 27%. During the same time, our area saw robberies increase 50% from 155 to 233. Here's how the numbers plot out year by year...

Reported robberies each year from 2001 (left) to 2012 (right).


• Taking a look at only the period of January 1 through June 3 of each year, robbery reports in the area were 62% higher on June 3, 2013 than on June 3, 2001.  But wait! We've finally found it! We've found a statistic that shows crime is technically down in Wrigleyville and Boystown: 2013 is currently four robberies shy of last year's June 3 tally. So, the 19th district's much ballyhooed "crackdown" on robberies can take credit for a reduction of, ahem, four incidents. Cialis anyone?
Reported robberies as of June 3 each year from 2001 (left) to 2013 (right).
Now, for the eggheads:

Methodology
Historic crime data provided by the City of Chicago for the current 19th police district as well as the former 19th and 23rd police districts were collected. The old 19th and 23rd police districts were combined on March 4, 2012, to form the current 19th district.

We extracted all robberies from the above data.

We filtered the robbery data, reducing it to incidents that occurred within the boundaries of the police department's current beat numbers 1923, 1924, and 1925 as shown on the map above*.

*Full disclosure: The lines that divide Chicago police beats literally run down the middle of their shared streets. So, crimes that occur on the south side of Irving Park Road's yellow stripes are in beat 1923 or 1925 while crimes that occur on the north side of Irving Park Road's center line are not.

It's easy to determine which beat should get credit for crimes that took place after the old 19th and 23rd districts merged on March 4, 2012. Unfortunately, it is not possible to determine with certainty which side of the street crimes took place on under the pre-March 4, 2012, beat structure. The city does provide latitude and longitude coordinates for most reported crimes, but the coordinates are not precise enough to reliably determine which side of the street was the scene of the crime.

In order to maintain consistency across all years, we have included all robberies that were reported on both sides of the border streets (Irving Park Road, Southport Avenue, and Belmont Avenue) in our calculations. As a result, our post-March 4, 2012, stats may vary slightly from "official" numbers.

1 comment:

  1. Just like an appliance manufacturer changes model numbers so Consumer Reports and Epinions can't track it, the CPD, determined to remain in denial to bamboozle the public, at least on the North Side, redraws boundaries so that only a statistician can track anything for 10 years.

    ReplyDelete