The overall crime rate fell 8% in Colorado in 2008 from 2007, and more in Denver. "Colorado's overall crime rate dropped last year for the third time since 2005[.]" Colorado did better than the nation as a whole which also had falling crime rates. Crime rates are less cyclical than most people believe them to be.
Car theft was down 22%, which makes sense. The Denver Post interviewed a law enforcement officer and got a law enforcement answer to the question of why car theft has declined so much: more DNA testing at property crime scenes. The answer is very likely wrong, however. DNA testing is more common in burglaries which haven't fallen nearly so much. A better explanation is simpler. Demand for cars of all types, new and used, is way down, and used cars are cheaper as a result. Reduced demand for cars means reduced demand for stolen cars. And, why steal what no one wants to buy from you?
They didn't offer the decline percentages for the entire period of falling crime since 2005, but overall, the drop is very significant.