Unlike solving violent crimes, cracking down on drug offenses can net serious money for police departments. Radley Balko links that finding to some troubling stats:
A drug offender is much more likely to be arrested in Chicago than he was 10 or 20 or 30 years ago. But kill someone in Chicago, and you're only about half as likely to be caught as you were in the early 1990s.
Thoughts from a Chicago-area cop here.