Where do robbers choose to locate?

Rob thy neighbor appears to be the decision rule for robbers, at least in Chicago. Bernasco, Block and Ruiter, writing in the January 2013 issue of the Journal of Economic Geography, present research on robbers’ choice of crime sites:

“This article analyzes how street robbers decide on where to attack their victims. Using data on nearly 13,000 robberies, on the approximately 18,000 offenders involved in these robberies, and on the nearly 25,000 census blocks in the city of Chicago, we utilize the discrete choice framework to assess which criteria motivate the location decisions of street robbers. We demonstrate that they attack near their own homes, on easily accessible blocks, where legal and illegal cash economies are present, and that these effects spill over to adjacent blocks.”

The graph below (on p. 129 in the paper) illustrates robbers’ tendency to carry out their activities closest to where they live (for reasons why see the paper).

crime location

crime frequency and distance from robber residence

The findings are at once obvious and insightful. The insightful bit is that because of the geographic concentration of crimes and criminals, sometimes it might make more sense from the point of view of authorities to just focus on containing criminal activity within specific neighborhoods, leading to further entrenchment of a culture of crime in those neighborhoods.

If you notice,  in most places – including Nairobi – certain types of crime only get reported when they cross these implicit barriers. Otherwise, crime in bad neighborhoods becomes a case of if a tree falls in the forest.

Defending Nairobi

The New York Times has a story on the security situation in Nairobi. In the interest of full disclosure, Nairobi is my home town. I was there this summer and would like to point out – just for the record – that although Nairobi may not be the safest place in the world, it is not the most dangerous city in the world either. The city has 4 million people, give or take. Income inequality is off the charts. The city’s economy cannot provide enough jobs for its youth, most of whom do not spend enough time in school and therefore resort to petty theft to earn a living. This summer there was a wave of kidnappings. Some were by real criminals. At least one that got exposed was by a young woman trying to get money from her father by pretending that she was kidnapped.The Nairobi city council is run by a bunch of clowns.

I agree with Gettleman that the incidence of crime in Nairobi is way too high. That said, Nairobi is not Jo’burg or Kabul. It is still very much a live-able city – as evidenced by the many NGOs and UN agencies that have set up shop in there.