Lott has an article in the National Review Online where he claims that the Washingtonian DC handgun ban caused crime increases:
Crime rose significantly after the gun ban went into effect. 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. During this same time, robberies fell from 1,514 to 1,003 per 100,000 and then rose by over 63 percent, up to 1,635.
I’ve graphed the homicide and robbery rates for the ten years on either side of the law so you can see how Lott cherry picked his numbers as usual. (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, Lott didn’t just choose one year at random. He chose 1981, which just happens to be the year that had the highest homicide and robbery rates of the ten following years.
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 drafted support for Lott’s claim that the law caused crime increases.
Over on his blog, Lott presents a graph showing crime rates. And it looks good for his case—it’s V shaped, with the bottom of the V right when the law was passed. Except that he graphed the overall crime rate. The majority of crimes are non-violent ones like larceny, where handguns are not a factor, even offensively or defensively. His graph isn’t even remotely relevant but if he graphed something relevant like homicide it wouldn’t support his case.