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April 18, 2007

Causation and Correlation

HowToLieWithStatistics.jpg brady_osama.gif

According to the Brady Campaign (formerly Handgun Control Inc.) Virginia is the second easiest state to get a gun in.

Nothing to confirm that, but this is a state that is pretty easy to get a handgun, according to the Brady Campaign to Prevent Gun Violence. You'll remember Jim Brady, who was shot in the head by John Hinckley at that failed assassination attempt in the early '80s. They say this is an easy state to get a gun in, only second only to the state of Georgia.

-Greg Hunter. CNN. April 17, 2007

I don't know how they decide something as subjective as "easy to get a gun." However, every year, the Brady Campaign publishes a "report card," grading states on a scale from A to F. An A means the state has enacted gun control laws favored by Brady. Osama bin Laden can legally purchase a machine gun without any paperwork -- or something like that -- in a state with a Brady F grade .

Brady's grades can bee seen at the web site StateGunLaws.org .

Thirty-two states received a "D" or an "F" grade measuring their state's gun laws, according to nationwide ratings released by the Brady Campaign to Prevent Gun Violence in partnership with state-based gun violence prevention organizations across the nation.

Virginia, which rations handgun purchases to one a month, earned only a C-.

Washington DC, which has banned private ownership of handguns since 1976, received only a B.

brady-va-2005.jpg brady-dc-2006.jpg

What the Brady Campaign doesn't reveal is how their grades correlate with actual crime rates.

Last October, ArmsAndTheLaw.com published a paper by Denton Bramwell which demonstrated the lack of correlation between the Brady grades and violent crime rates.

You can download his 2 page paper by right-clicking here or here, and selecting "Save As" or "Save Target As" from your web browser's drop-down menu. It's a small 40 KB .PDF file, so even those of you with a dial-up connection can download it quickly.

Since a picture is worth a thousand words, here's the two graphs from his study, plotting Brady Grades vs. crime rates:


Those of you with an intense interest in statistics may want to know that I also did a regression analysis on the data just to verify the tale of the graphs. The correlation between your state’s Brady grade, and its actual murder or violent crime rate is absolutely no better than you would get if you ran pairs of random numbers through the analysis.

In short, your chances of being killed, raped, or assaulted are, on average, no better, and no worse, in states that got the coveted Brady A or A-, than they are in states that got a D or an F. If the laws the Brady Campaign favors were very successful in combating violence, you could not possibly get this result.

-Denton Bramwell. "State Got a Poor ‘Brady Gun Grade’? Don’t Rush to Pack Your Bags."

If those graphs were targets, I'd consider it poor shooting.

The only criticism I really have is that Bramwell does not tell the reader what year, or years, his data is from. I did a similar plot of Brady grades vs. crime rates several years ago, but without the "regression analysis" -- I think I used to know what that means -- and got similar results.

Posted by Robert Racansky on April 18, 2007 at 8:42 PM


In Israel and Switzerland a license to possess guns is available on demand to every law-abiding adult, and guns are easily obtainable in both nations. Both countries also allow widespread carrying of concealed firearms, and yet, Switzerland and Israel have rates of homicide that are low despite rates of home firearm ownership that are at least as high as those in the United States.

But, of course, both Israel and Switzerland would have received F rating on the Brady scale...

Posted by: Uzi on April 19, 2007 at 9:04 AM

Whoo-Hoo! My home state gets a passing grade:


New Mexico Receives an "F" on Laws Shielding Families From Gun Violence


And, yeah, I carry!

Posted by: robohobo on April 19, 2007 at 10:43 PM

Israel and Switzerland would have received F

Which explains why you left Israel for Illinois (Brady grade: A-). Right?

Posted by: Robert on April 20, 2007 at 6:49 AM

I had no idea whatsoever...

Posted by: Uzi on April 21, 2007 at 12:30 PM

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