In the Windy City, prostitutes sleep with police more often than get arrested by them

Another dispatch on the Freakonomics effect: University of Chicago economist Steven Levitt (Mr. Freakonomics himself) and his collaborator Sudhir Venkatesh, a Columbia University sociologist who previously worked with Levitt to measure the average wages of street-level drug dealers (pdf), have teamed up to study the economics of street prostitutes in Chicago.

Their recent working paper (pdf), which they presented at this weekend's ASSA conference (the yearly get-together where social scientists from around the world preview their research) in New Orleans, is based on surveys conducted with prostitutes and pimps in Chicago neighborhoods and incident data from the Chicago Police Department. The findings? Street prostitution yields an average wage of $27 an hour, hardly worth it considering the extraordinary occupational hazards.

What's particularly interesting is the authors' section on bargaining and the law. They estimate that roughly 3 percent of all tricks performed by prostitutes who aren't working with pimps are freebies given to police to avoid arrest. In fact, prostitutes get officially arrested only once per 450 tricks or so, leading the authors to conclude that "a prostitute is more likely to have sex with a police officer than to get officially arrested by one." When freebies given to gang members are factored in, about one in 20 tricks go solely for protection and the "privilege" of plying their trade.

The most depressing news is the woeful lack of condom use. Just as with recent studies of Mexican and Indian prostitutes, Levitt and Venkatesh find that payments go up substantially when condoms aren't used. And plenty of johns are apparently happy to pay the premium: Condoms only get used about 20 percent of the time, the authors estimate. Some protection, it seems, is worth a freebie; others go out the window for a few extra dollars.