The short answer is no. "There is no clear and highly predictable relationship between economic variations and the rates of life-threatening crime," said Franklin Zimring, William G. Simon Professor of Law at UC Berkeley. Zimring pointed out that crime can rise at the same time as economic prosperity (as it did in the 1960s and early 1970s), but it can also fall during times of economic distress (as it did in the early 1980s).

Zimring also cautioned against making predictions based on last year's startling decline. "We're not in a sustained decline," he said. "This is good news on a relatively short fuse, not like the nine-year crime decline of the 1990s. Nobody knows what happens next month."

Criminologists now discourage looking at any one theory to explain away shifts in crime rates. From demographics to drugs to incarceration policies, they've all proven to be inadequate to the task, said Barry Krisberg, Distinguished Senior Fellow at UC Berkeley School of Law. "Ultimately you're trying to model individual decisions by millions of people," Krisberg said. "It's very, very difficult."

What now makes sense, Krisberg added, was attempting to strike a balanced policy approach. "We're recognizing that the response to crime has to be multi-dimensional," he said. "You need early childhood development and you need police to go and stomp out the bad guys and you need street outreach workers to go out and cajole the people on the fence. But striking the right balance of those elements is key."

What also makes sense now is better research. Considering the importance of crime to everyone's quality of life, why haven't we made figuring out the best methods of crime reduction a national project? This should be an easy area for bipartisanship, but apparently politicians simply don't care about it very much: the National Institutes of Health spend about $400 million annually on dental research, while the National Institute of Justice spends about $50 million annually on criminal justice research.

For example, most experts agree that it's not the number of police officers on the street but the way that they're trained and deployed that makes a difference. Zimring noted that street policing, also known as community policing, seems to be a better investment than it looked like 20 years ago, and that "the Bay Area has to play catch-up to other cities" when it comes to the technique. But ultimately, there hasn't been enough research done on the impact of different policing strategies to say that community policing is a silver bullet. It may depend on the community, the year and a host of other factors that are impossible to control.

In order to get the answers we need, it's going to take political leadership - and politicians who are mature enough not to make crime into an ideological talking point. But who knows when that will happen? For now, it might be best just to enjoy our safer streets - and to hope that they stay that way.