Today I've been looking at crime trends in California. I stopped by the Attorney General's Crime Analysis Center and quickly made the table below, which is official crime data for a nine year period.
You can click on the table image to make it bigger:
Over the entire nine year period, the rate of crime (per 100,000 population) has declined 22.5 percent from 1994-2003, from 2,353 to 1,823 (a difference of -530; when 530 is divided by the base year of 2353 the percent change is -22.5). The greatest decline has been in property crime (-32.2 percent), but there are also sizeable reductions in violent crime (-24.4 percent), drugs (-18.5 percent), and a slight decline in all other offenses (-4.4). In contrast, there has been an increase in sex offenses (+14).
On the other hand, if you only look at the most recent annual (2002-2003) change the results are more mixed. For example, the overall rate of crime has increased, not decreased, particularly for drug, property and all other offenses. However, there are decreases in violent and sex offenses.
What are we to make of these data--is there overall decline but mixed short-term changes that one ought to keep their eye on? In answering this question we could consider how much relative emphasis to give to long-term vs. short-term changes; to differences in trends by offense type; to the question of how we balance this discussion with known deficiencies of official data, such as the huge issue of whether these changes are a result of changes in priorities and resources of law enforcement and/or the operating rules of statistics collectors and reporters. And then there is the matter of media coverage of crime, which by subjective assessment in California recently and more objective studies done elsewhere appears uncorrelated with official data on crime.