Wednesday, March 25, 2009

Oakland vs. California Crime

When I saw the disparity in crime rates between Oakland and other mid-size CA cities, I asked the question "Were we always different? If not, when did we pull away?" Consequently, what I really wanted to do was compare to the other mid-sized cities (Fresno, Sacramento, Long Beach, Anaheim, Santa Ana). But that's a lot of work, and not every city (or the FBI) provides historical crime data online going back before 2000, and I suspect there are people who know either where to find the data already digested, or at least in an easier format - if so, please feel free to comment.

So what I settled for was looking at whether Oakland followed the trends in homicide and general crime across the state. I used both California vs Oakland homicide, and composite crime as an indicator. To get the curves in the same region of the graph I normalized Oakland to CA in 1969, and I had to use some pretty extreme multipliers as you can see. Sources and caveats at the end; click on the graphs to make them legible.

The murder rate, in terms of the trend outpacing the rest of the state, is a relatively recent trend. From 1969 until 1991 the overall murder rate in Oakland did not rise as quickly as in the rest of the state, as a percentage of the 1969 rate, and then at the peak in 1992 it dropped slightly faster. However, just in 1999 it began to shoot up while the rest of the state rose only very slowly.

Similarly, the general crime rate in Oakland does not rise as quickly as a percentage of the 1969 rate as the California rate does. However, in 2000 when crime in the rest of the state was still falling from its peak in 1992 (and continued to until at least 2006), Oakland began climbing. Again, outpacing the rest of the state is a recent trend.

It bears keeping in mind that both the murder rate and the general crime rate peaked in 1992 in both California and Oakland, and we haven't returned to those levels. But that we see a spike beginning in 99-2000, not only while the state trend is declining but prior to the dot-bomb downtown, strongly suggests something specific to Oakland is going on.

Sources and Caveats:
(1) California homicide and crime data from the California Attorney Generals Office. To avoid holes in the graph data was smoothed between 4-year-data points.
(2) Oakland population data 2000-2007 from the Census.
(3) Oakland population data 1960-1980 from the Census, obtained here.
(4) Oakland population data 1990 from the Census, obtained here. Population was assumed to increase or decrease arithmetically between census points.
(5) Oakland absolute crime data comes from OPD.
(6) The Oakland general crime statistic is a sum of all murders, forcible rape, robbery, felony assault, burglary, total larceny, and auto thefts. The California general crime statistic is a sum of all homicides, rapes, robberies, and aggravated assaults.
(7) Data for Oakland general crime statistic 1995 was unavailable, so figure was averaged from 1994 and 1996.

No comments:

Post a Comment