Crime Doesn't {{Insert Variable}}

Tuesday, September 17, 2013


There's no citywide relationship between crime rate and elevation in San Francisco. It's because there are other factors at work - like property value, income, tourism, etc. - in between the two. But there are a few discrete spots around the downtown area where it is at least partially accurate to say "Crime doesn't climb" - check out the last map on this page.

Crime Doesn't What?

Dammit, I love hexbins. I love their flow complexity, I love their visual appeal, I defend them where necessary, and I use them wherever I can. However, sometimes hexbins don't tell the whole story.

Last week a couple of talented Bay Area developers put some of San Francisco's new open data to use, testing the old adage that "Crime Doesn't Climb" in the city. They compiled SFPD crime statistics in elevation-based strata and found - indeed - that the lion's share of SanFranCrime occurs closest to sea level. Recognizing a bit of simplicity in this argument, they went a step further and adjusted the numbers to account for the fact that there is simply more space - more crime-canvas, if you will - at lower elevations. The results were the same: lots of crime low, not much up high.

The web reacted with characteristic nuance and reason:

While there's irony and sarcasm at work here, I think it would probably be a shame if even a handful of people now contented themselves with the certainty that criminals are lazy, or if some misguided readers resolved only to pass through SoMa in an armored car.

Because at it's heart, this analysis has already been critiqued by Randall Munroe:

Crime occurs where people - perpetrators and victims - are already concentrated. As such, any explanation of when/where/why has to account for population.


The best level of detail available on population is the U.S. Census block. In a city as big as San Francisco, there are thousands of these, each with a very credible population count. They're not as spatially consistent as hexbins, but they're accurate:


Elevation variation also contributes to the city's distinct character:


And the frequency of crime seems to reflect a bit of both population and elevation:

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