How Obama Reduced Crime Rates Last Year

President Obama surely didn’t intend it, but he deserves some credit for last year’s 7.4 percent drop in murder rates. His election caused gun sales to soar, and crime rates to plummet.

While gun sales started notably rising in October 2008, sales really soared immediately after Mr. Obama won the presidential race. 450,000 more people bought guns in November 2008 than bought them in November 2007, that’s over a 40 percent increase in sales. By comparison, the change from November 2006 to November 2007 was only about 35,000. Over the last decade, the average year-to-year increase in monthly sales was only 21,000.

The increase in sales continued well beyond November 2008. From November 2008 to October 2009, almost 2.5 million more people bought guns in the 12 months after the election than in the preceding 12 months. The National Instant Criminal Background Check System, or NICS, doesn’t tell us how many guns each person bought just the number of people who bought them. Most likely though, gun sales rose by more than the number of people who purchased them.

At the same time gun sales were soaring, there was an unusually large drop in murder rates. The 7.4 percent drop in the murder rate was the largest drop in murder rates since the 1999. For those who don’t remember, 1999, when President Bill Clinton and Columbine occurred, was another time when gun sales soared. With people such as Elena Kagan serving as Mr. Clinton’s deputy domestic policy adviser were pushing hard for more gun control, Americans were worried that more gun bans were coming. And in response gun sales soared.

Just as higher arrest and conviction rates, longer prison sentences, or the more frequent use of the death penalty reduce crime, so does letting victims defend themselves with guns. More certain or greater penalties make it more risky for criminals to commit crime. Victims who can defend themselves can also make committing crime more dangerous and deter criminals.

Americans living in the District of Columbia and Chicago have seen this phenomenon themselves. After the ban went into effect in both cities, murder rates rose dramatically. After the Supreme Court threw out DC’s ban and gunlock laws in 2008, the District’s murder rates plunged by 25 percent in 2009. Indeed, my research in the just released third edition of More Guns, Less Crime shows that every place in the world that we have crime data for has seen murder rates climb when guns were banned.

If Mr. Obama really understood that letting law-abiding citizens defend themselves reduces crime, it is unlikely that gun sales would have had to increase. Yet, if the Supreme Court strikes down the Chicago gun ban this month, Americans may get to see yet again that more guns mean less crime.

John R. Lott Jr. is a FOXNews.com contributor. He is an economist and the author of "More Guns, Less Crime (University of Chicago Press, 2010), the third edition of which was published in May.".