Lott (along with Eli Lehrer) has an editorial in the Washington Times which claims that the 1976 gun ban caused crime to increase.
D.C. residents need more protection: Crime has risen significantly since 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. In fact, the murder rate after 1976 has never fallen back to what it was in 1976. Robberies and overall violent crime changed just as dramatically. Robberies fell from 1,514 to 1,003 per 100,000 and then rose by over 63 percent, up to 1,635.
If you look at the graph you will see the trick that Lehrer and Lott have played. I’ve graphed the homicide and robbery rates for the ten years on either side of the law so 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.