John Lott’s newest piece at Investors’ Business Daily starts this way:
Do fewer guns mean fewer firearm deaths? If you believe the March 6th issue of the Journal of the American Medical Association of Internal Medicine, the answer is “yes.”
A study by Eric Fleegler and four other co-authors received massive national news coverage from USA Today to the television networks.
But the report is based on embarrassingly bad statistics that are rigged to get the result the authors wanted.
Take how they measure gun ownership. Believe it or not, this study measures gun ownership by looking at the share of suicides committed using firearms.
Then the authors go on to commit an egregious and basic statistical error. They claim that states with higher gun ownership have higher gun death rates. But wait a second — most gun deaths are gun suicides. And what they call “gun ownership” in their study is also measured by gun suicides.
In other words, all the study proves is that more gun suicides leads to, well — more gun suicides. Any serious statistical journal would not have published such nonsense.
The Fleegler study also involves a geographic comparison across the 50 U.S. states . . . .
A link to the Fleegler article is available here. Few papers create this arbitrary sum of gun laws to as a measure of how restrictive state laws are. What most studies do is take each individual law and simultaneously account for them separately. That way you can see which laws count and which ones don’t. Otherwise, there is a lot of arbitrariness in terms of what gun laws are included in creating that sum. By excluding or including different laws one can alter the over all ranking of states. Here is an example of the arbitrariness of how their gun law measure is created:
This “1 law = 1 point” score gives each law equal weight. However, the Brady Center also prepares an empirical weight schema for each set of laws, scaling the scores out of 100 points and giving additional weight to laws believed to be more important. In their weighted scoring system, the “strengthen Brady background checks” category (which includes requiring universal background checks on all firearm purchases no matter who sells the firearm and requiring permits to purchase firearms) receives the greatest number of points. We separately analyzed the data using this weighted scoring system. A detailed description of each of the laws and the weighted scoring system is available from the Brady Center. . . .
Other problems include trying to explain murder rates without any measure of law enforcement and looking at purely cross-sectional data. Below is part of a long discussion in The Bias Against Guns, Chp. 5 on why few researchers use purely cross-sectional data (More Guns, Less Crime also has a long discussion in Chp. 2).
Unfortunately, many contemporary discussions rely on misinterpretations of cross-sectional data. The New York Times recently conducted a cross-sectional study of murder rates in states with and without the death penalty, and found that “Indeed, 10 of the 12 states without capital punishment have homicide rates below the national average, Federal Bureau of Investigation data shows, while half the states with the death penalty have homicide rates above the national average” (Raymond Bonner and Ford Fessenden, “States With No Death Penalty Share Lower Homicide Rates,” New York Times, September 22, 2000, p. A1.). However, they erroneously concluded that the death penalty did not deter murder. The problem is that the states without the death penalty (Alaska, Hawaii, Iowa, Maine, Massachusetts, Michigan, Minnesota, North Dakota, Rhode Island, West Virginia, Wisconsin, and Vermont) have long enjoyed relatively low murder rates, something that might well have more to do with other factors than the death penalty. Instead one must compare, over time, how murder rates change in the two groups – those adopting the death penalty and those that did not.
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