Friday, September 20, 2013

20 wounded, 3 dead on Thursday: Are Chicago homicides really down?

Thursday was a bad night in Chicago. The evening saw 23 Chicagoans shot, 3 of whom did not survive their injuries. Of those 23 shootings, 13 occurred in a single incident with a single shooter. That last one made national news, both because of the sheer brazenness of the attack and his choice of weapon. I hear a lot of people say that gangs in Chicago are armed with AK-47s and regularly use them in attacks, and although that's almost always hyperbole, in this case they would be right. The Cornell Square Park shooting saw a single shooter, likely gang involved, open fire on a crowded basketball game with an AK-47. Witnesses confirmed the weapon and police confirmed the 7.62 mm shell casings on the scene. Add that to the 10 other people shot across the city and you have an abnormally bad Thursday leading into what promises to be a predictably bloody weekend.

Was Thursday's bloodshed indicative of a more general trend in Chicago violence? Are things as bad as they look? CPD Superintendent Garry McCarthy and Mayor Rahm Emanuel don't think so. Both men made statements on Friday about the Cornell Square incident, underscoring the tragedy but emphasizing the city's ongoing efforts to curb shootings and lower crime. McCarthy refused to let Thursday's attack undermine the work that his Department has been doing, with the Tribune stating "McCarthy argued Friday that the statistics were old news and did not represent the progress made in the city, where the murder rate has dropped by 20 percent over the past year."

McCarthy's claim is not a new one. For months, the City has been touting a historic decline in homicides, with April's count standing out as the lowest in decades. And to be sure, there is statistical reason to believe his claim. As of September 1st of last year, Chicago had suffered 366 homicides. In 2013, we were "only" at 287, and that does represent the 20% drop that McCarthy cites. But does that drop hold up over a multi-year perspective?

We can obtain a little perspective on McCarthy's 20% drop by looking back over a longer period of time. No one cares if Chicago improves from year-to-year. We care if those improvements are enduring ones over a longer period of time. The table below gives monthly homicides for the past 7 years. Data only goes through September 1st of any given year. Homicide totals represent all murders from the 1st of the month to the last day, and cumulative totals are given at the end of each column. Looking at the 2013 column, I have highlighted values based on their relationship with 7-year averages for each month. Red highlighted values were unusually high (1+ standard deviation over the average), Green values were unusually low (1+ standard deviation below the average), and Blue values were about average for the period.

2007-2013 Chicago homicide totals
through September

2013 201220112010 2009 2008 2007
January 43 402820243522
February 14 292525262021
March 16 522231213537
April 24 413048414734
May 44 513948474835
June 43 474654455349
July 51 495842586645
August 52 573760515146
TOTAL 287 366285328313355289

(Why not a 10 or 20-year perspective? The 7-year lens is partially based on patterns of crime across the city. There was a marked shift in the types of crime that occurred between 2005 and 2007, both based on the overall economy, Chicago Housing Authority demolitions, policing, gang fragmentation, etc. This is an example of trying to inform a quantitative dataset with qualitative observations)

The biggest takeaway from this table is that 2013's total numbers are suspiciously similar to those of 2010 and 2007. That's worrisome because both of those years, although individually lower in homicide totals, did not signal a reversal of the Chicago crime tide. 2007 preceded the awful 2008, a year which saw consistently high homicide totals throughout the entire summer. July 2008 was the worst July since the early 2000s. So although 2013 is a marked improvement from 2012, there is little to suggest that it signals a broader shift in the cycle of Chicago murders. Next year might look like 2009 or 2011. Or it could look like 2008 all over again.

There is also a more sinister conclusion that we might draw from the table. Homicides between February and April of 2013 were at historic lows, indicated by the green lettering. But starting in May, homicides climbed back up to their average values (indeed, they are slightly above average for the period). Now we find ourselves in September where our annual total is back to what it was in 2010 and 2007. This may suggest that whatever factors kept crime down in February-April stopped having an effect in May. Weather is one explanation; April alone saw the most rainfall in over a century, and not even criminals want to be outside in a Chicago downpour. Policing is another. McCarthy and Emanuel have been advertising their hot-spot policing strategies (and a dozen other strategies) for months now. And of course, there are a half dozen other explanations that might account for the drop, including subtle economic or housing shifts, fluctuations in drug markets, incarceration and the incapacitation effect, and so on. But whatever those factors might have been, they were not sufficient to keep crime down starting in May. 

Chicago crime is obviously too big of a monster to discuss in a single post. Just discussing citywide homicides barely qualifies as an analysis, let alone a comprehensive and decisive one. The street-level patterns of policing, shootings, drug markets, personal disputes and drama, cliques, and countless other factors all need to be considered in assessing Chicago crime. Regardless of how you tackle the problem, however, a clear trend would almost certainly emerge from your investigations: Chicago is basically the same today as it was in 2007 or 2011. Next year might be the same as this year. Or it might be another 2012.

This all gives us a little perspective both on McCarthy's claims and on the Cornell Park shooting that led off this article. On the one hand, McCarthy isn't fooling anyone when he talks about a lowered homicide rate, although no one can blame the man for trying to inspire public confidence in his officers and strategies. But on the other hand, no one should look at Cornell Park and declare that Chicago is in a state of emergency. Certainly, no one should be calling for the National Guard, although that will inevitably come. Chicago is more or less the same as it ever was, which should be as much cause for bitter relief as it is for justified anger.

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