Gun laws are strict in Chicago. In fact, until 2010, there was an outright ban on handguns. But you wouldn't know it from the number of firearms seized in crimes and unpermitted uses in 2012 (7,400 to New York City's 3,285), to say nothing of the city's staggering gun violence.


"Not a single gun shop can be found in [Chicago] because they are outlawed," reads this piece in yesterday's New York Times. But then where are all the guns coming from? The graphic up top, which visualizes the provenance of about 50,000 firearms recovered by the Chicago Police Department between 2001 and 2012, gives us some idea. According to Kevin Quealy and Tim Wallace of The New York Times, more than half of those guns originated outside the state of Illinois, and came from all 50 states.

You might ask why this is posted on a science blog. Datavisualizations like these are a handy resource when it comes to communicating statistics on things like gun violence to lawmakers. They're an indispensible tool to law enforcement tasked with tracking illegal gun trafficking. When mapped over several years, or visualized at a county-by-county resolution, data transformed into figures like this allows for patterns to emerge and insights to be made that might otherwise go unnoticed. This is statistical analysis made useful and compelling.


The numbers and patterns seen here are of particular interest to policymakers in light of the Sandy Hook shooting (and others). Gun rights advocates, not surprisingly, are especially keen on visualizations like these, because they suggest that even the strictest firearm laws can be unsuccessful at curbing gun violence. Is this actually the case? The answer is less cut and dry than this figure might suggest, but the answer, one way or another, is surely somewhere in the numbers.

Visit the New York Times for a more comprehensive breakdown of this and other maps of Chicago's gun's origins.

Graphic by Kevin Quealy and Tim Wallace