Digital Government Transformation

Crime Over Time: Visualizing Crime Data in Chicago

At what time of day do most kidnappings occur? What’s the most crime-ridden day of the year? Is prostitution more of a weekday occurrence, or a weekend one?

We grabbed the crime data from 2001 to 2013 from Chicago’s Socrata-powered open data site and stuck it into Statwing to make it easy to analyze. It’s fun stuff:

Daily rhythms of crime

Take a look at the daily cycles of various kinds of crime, roughly ordered by how early in the day the crime tends to happen:

daily rhythm of crime in chicago

 To see other crimes’ daily rhythms, take a look at this data in Statwing.

Weekly rhythms

Before you look below, try to guess: Which of these crimes is mostly heavily associated with weekdays instead of weekends: property damage, prostitution, narcotics, or burglary?

Here’s your answer:

weekly rhythms of crime in chicago The weekly rhythms of crime in Chicago

By far the clearest trend is that prostitution tends to occur on weekdays (or at least, people tend to get arrested for it the most on weekdays). 

To see other crimes’ weekly rhythms, take a look at this data in Statwing

Annual rhythms of different crimes

Here’s the annual pattern of crime in Chicago, again with data from 2001 to 2013:

annual rhythm of all crimes in chicago over timeAnnual rhythm of all crimes over time

The spikes on the first of each month are probably a data quality issue, but the spike on New Year’s Day and the dip on Christmas are real.

Narcotic arrests look pretty similar, except with little dips for New Year’s Day, the Fourth of July, and Halloween:

narcotics arrests in chicagoNarcotics arrests

Most gambling arrests in Chicago are for playing dice. Presumably it’s a bit too cold to play dice on the street during Chicago winters:

gambling arrests in chicagoGambling arrests

Sadly, criminal sexual assaults are strongly associated with New Year’s Day:

criminal sexual assaults in chicagoCriminal sexual assaults

Homicides, like gambling, are most common in the warmer months:

homicides in chicagoHomicides

For a very in-depth look at the relationship between heat and crime in Chicago, check out Brian Keegan’s great work on the subject.

To see the weekly rhythms of other crimes, take a look at this data in Statwing.

Trends over time generally

Like most cities, Chicago has recently seen a decline in crime:

total number of crimes per year in chicagoTotal number of crimes per year

This applies to homicides as much as to any other crime:

homicides in chicagoHomicides in Chicago

Interestingly, though, the proportion of homicides that end in arrest has dropped sharply:

percent of homicides that result in an arrest in chicagoPercent of homicides that result in an arrest

Note that this doesn’t necessarily mean Chicago police are solving fewer homicides, just perhaps making fewer arrests of innocent people (though Chicago’s rate of solving murders isn’t particularly stellar). 

To see which crimes have actually gone up, despite the overall downward trend, take a look at this data in Statwing.

We hope you enjoyed this. And if you did, please share it. Cheers!

Statwing makes statistical analysis delightful and efficient. Think of it like a more powerful form of spreadsheet pivot tables, or an intuitive, modern version of traditional statistical software. Go to Statwing to try out other demonstration datasets or start a free trial.


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