Left Rudder

Every couple of years or so, Mary RoshJohn Lott is compelled to recycle the long discredited notion that DC’s gun laws caused an increase in homicide and crime.

Via yet another gunloon blog that bans dissenting views, John Lott trots out the tired old chestnut for another spin ’round the gunloon:

The problem for the city is that anyone who can look up the crime numbers will see that D.C.’s violent crime rate went up, not down, after the ban.

[…]

The city’s brief focuses only on murder rates in discussing crime in D.C. Yet, in the five years before Washington’s ban in 1976, the murder rate fell from 37 to 27 per 100,000. In the five years after it went into effect, the murder rate rose back up to 35. But there is one fact that seems particularly hard to ignore. D.C.’s murder rate fluctuated after 1976 but has only once fallen below what it was in 1976 (that happened years later, in 1985). Does D.C. really want to argue that the gun ban reduced the murder rate?

Similarly for violent crime, from 1977 to 2003, there were only two years when D.C.’s violent crime rate fell below the rate in 1976. These drops and subsequent increases were much larger than any changes in neighboring Maryland and Virginia. For example, D.C.’s murder rate fell 3.5 to 3 times more than in the neighboring states during the five years before the ban and rose back 3.8 times more in the five years after it. D.C.’s murder rate also rose relative to that in other similarly sized cities.

This is what’s known in the biz as “cherry-picking.” Tim Lambert debunked Rosh Lott in 2003; the same graph he used then applies here:

As Lambert explains:

…you can see the trick Lott has used. (Data is from here.) Notice how the crime rates fluctuate from year to year. If you choose one year at random to represent the situation after the law was passed their is a good chance that it will be unrepresentative. Of course, they didn’t just choose one year at random. They chose 1981, which just happens to be the year that had the highest homicide and robbery rates of the ten following years. (And contrary to their claim, the murder rate in 1985 was below the 1976 rate.)

Also by presenting rates for just 1971 and 1976, they make it look as if the rates were decreasing before the law, instead of going up and down. The law was also in effect for only part of 1976, so that year is not a good choice to represent the situation before the law.

If you look at the graphs you will see that homicides tended to be lower after the law and robberies were about the same. Of course, just looking at the graphs only gives a rough idea of the possible effects of the law. This has been studied by several researchers. Loftin at al (NEJM 325:1615-1620) found significant decreases in firearms homicides and no significant change in non-firearms homicides. Kleck et al (Law & Society Review 30(2):361-380) disputed their findings, arguing that the law had no effect. Whoever is correct, there is no published support for Lehrer and Lott’s claim that the law caused crime increases.