After a night out with friends (bloggers Megan McArdle and Peter Suderman), blogger Matthew Yglesias was assaulted:
But then lo and behold right by Catania Bakery a couple of dudes ran up from behind, punched me in the head, then kicked me a couple of times before running off. Once, years ago, in Amsterdam a guy threatened me with a knife and took my money. These guys took nothing, and just inflicted a bit of pain.
I sympathize deeply with Matthew. Something similar happened to me when I was just a bit younger than Matthew is now (jumped by three guys after an evening out with friends) albeit with a different outcome. I think he might want to seek out some counseling: being the victim of a crime, particularly a violent crime can have consequences that don’t become apparent until much later.
However, I have very little sympathy with his observation:
To offer a policy observation, higher density helps reduce street crime in an urban environment in two ways. One is that in a higher density city, any given street is less likely to be empty of passersby at any given time. The other is that if a given patch of land has more citizens, that means it can also support a larger base of police officers. And for policing efficacy both the ratio of cops to citzens and of cops to land matters. Therefore, all else being equal a denser city will be a better policed city.
Since Durkheim wrote about crime as a social phenomenon more than a century ago it has been believed that higher density meant more crime not less. I don’t believe there’s a simple correlation; however, I think the evidence is overwhelming that some factors (population density, young population, transient population, unemployment and underemployment, etc.) are positively correlated with higher crime rates and that the larger the city the more likely these factors are to be the case. There are volumes of studies to that effect.
Are large cities “better policed”? I think the evidence of that is equivocal.
If you define “better policed” as more police officers per 1,000 residents cities of 250,000 population or more have, on average, 2.5 fulltime police officers per 1,000 residents while cities of 1,000 to 2,499 population have 2.6 fulltime police officers per 1,000 residents. That’s no great difference, it doesn’t really explain the lower crime rates in small towns, and it certainly doesn’t support the idea that lots more police officers means less crime.
Here’s a quote from Tony Bouza, formerly police chief of Minneapolis:
“Cops have nothing to do with the crime rate, and anyone who says so is an idiot,” he said. “They’re irrelevant to preventing crime — they just displace it to another area. And society can produce criminals at a much faster rate than the police can arrest everyone they can find.”
I also seem to recall a study (done in Kansas City? Omaha?) some years ago. In the study three precincts with similar demographics, density, building patterns, and crime rates were selected. In one precinct the number of policemen assigned was cut in half, in another it was left the same, and in the third it was doubled. Six months later no changes in the crime rates were observed. If I actually put my hands on the study I’ll cite it but I remember it vividly.
I don’t draw the conclusion from this that the number of police officers related to the number of residents is irrelevant; I conclude that there is no simple relationship between crime and population or population density.
Something that I think it’s important to remember: bureaucracies do not grow linearly. They grow greater than linearly and, consequently, a larger police force is significantly more expensive on a per capita basis than a smaller one.
I could also critique Matt’s assumptions about traffic and policing but I think I’ll stop there.
Therefore, while I sympathize with Matt very deeply I’m pretty skeptical about his prescription for reducing crime. I’d like to see some more evidence.
Update
I am reminded of Jane Jacobs’s hypothesis back in the 1960s of an inverse relationship between crime and population density and, indeed, there’s some evidence to support that:
Since most of the studies reviewed used data that were aggregated to a larger geographic area, it was suspected that the precision inherent in more disaggregated data would allow differences in urban and suburban areas to be teased out. Thus, the Jacobs (1961) hypothesis was adopted for the urban area and the converse hypothesis was put forward for the suburban area.
Instead, the results show that when layered onto more traditional predictive (sociodemographic) variables, population density at the census block group level is a
significant negative predictor of violent crime in both types of development, as well as in the county as a whole. Therefore, the Jacobs hypothesis, which was developed in distinctly dense urban areas of the Northeastern U.S., is supported in very diverse settings. Importantly, this environmental characteristic – population density – predicted more of the variance in violent crime than the majority of the other population characteristics in the model. The magnitude of this environmental characteristic represents an important theoretical contribution to the violent crime literature—namely that at extra-individual scales, environments are more powerful determinants of violent crime than the population characteristics that are traditionally examined.
However, Population Growth, Density and the Costs of Providing Public Services, by Helen F. Ladd in Urban Studies, Vol. 29, No. 2, 1992 notes that public safety spending per capita rises with population and that for most settings more population density equals more per capita costs to government
I see that this subject has caught James Joyner’s eye as well.
