"...a prostitute is more likely to have sex with a police officer than to get officially arrested by one."

Reason Magazine - Hit & Run > But Whatever You Do, Don't Legalize It:

"A new study by Freakanomics guru Steven Levitt comes to some uncomfortable conclusions about prostitution in Chicago. First, Levitt finds that prostitutes are more likely to have sex with city police than they are to be arrested by them:

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."