Reader Matthew Yglesias responds to a recent piece we posted on crime in the city. Want to add your own voice to this debate? Email Opinionist. 
Should the District respond to its high crime rates and current purported “crime emergency” by hiring more cops as several City Council members are proposing? Calm heads like DCist’s Martin Austermuhle say no and they have the numbers to prove it. He points out that DC has traditionally had a large police department — 742 officers per 100,000 residents in 1990, 631 per 100,000 residents in 2000, and that “if the police force were to grow to 5,000 officers, that proportion would increase to over 800 police officers per 100,000 residents, a shockingly high number.”
And, indeed, that would be a lot of cops. Low-crime New York City gets by with about 37,000 officers for the Big Apple’s 8 million residents — about 462 per 100,000 residents. On the other hand, per capita figures may not be the best way to think about the situation. New York’s 8 million people are packed into 321 square miles, giving it about 115 cops per square mile. The District is much less dense, giving us a much thinner police presence despite the higher cop-per-resident ratio — even if we boosted the DCPD to 5,000 officers from the current 3,800 we’d only have 73 or so per square mile.
It’s not clear, at any rate, how much light inter-city comparisons can shed. Adding cops reduces crime, but higher crime rates spur citizens to demand more police so the deterrent effect of large police departments doesn’t show up. What’s more, the MPD isn’t comparable to most other big city forces since much of its manpower is necessarily expended on federal security rather than conventional police work.
Fortunately, some very good evidence is on hand.
Jonathan Klick and Alex Tabarrok, economists at Florida State University and George Mason University respectively, took advantage of the much-mocked color coded terrorism alert system to shed some light on this important question. They examined daily crime rates in the District of Columbia between March 12, 2002 and July 30, 2003 a period during which the terror alert system oscillated between yellow and orange, noting that during the orange days police presence was about 50 percent higher than during the yellow ones. The result — a 6.6 decrease in citywide crime during high-police alert periods. Supporting the theory that this decline was attributable to the enhanced police presence, they found that the bulk of the reduction in crime came from Police District 1 — a 15 percent drop locally — where national monuments (and, therefore, terror-related manpower increases) are concentrated.
They conclude on the basis of this research that a 10 percent increase in police force size should produce an approximate 3 percent drop in the number of crimes, a result consistent with other economists’ analyses. Turning the DCPD into a 5,000-strong squad should, in other words, bring about a 9.5 percent reduction in crime. Based on 2005 crime statistics that would mean over 18 fewer murders, 330 fewer robberies, 360 fewer assaults, and 700 fewer stolen cars — that’s nothing to sneer at.
Matthew Yglesias is staff writer at The American Prospect and Associate Editor of TPM Cafe.
