2A - Decipher This 'Stand Your Ground' Study and Homicides
Stand Your Ground laws and homicides
by Andrew Gelman on June 27, 2012 in Judicial, Law
The Monkey Cage, Blog
Personally, I'm still working through the numbers and graphs - been a long day and the post (origional at The Monkey Blog) is dated, I have not seen it.
From the Post.....
.........The controversies surrounding Stand Your Ground laws have recently captured the nationís attention. Since 2005, eighteen states have passed laws extending the right to self-defense with no duty to retreat to any place a person has a legal right to be, and several additional states are debating the adoption of similar legislation.
Our results indicate that Stand Your Ground laws are associated with a significant increase in the number of homicides among whites, especially white males. According to our estimates, between 4.4 and 7.4 additional white males are killed each month as a result of these laws.We find no evidence to suggest that these laws increase homicides among blacks. Our results are robust to a number of specifications and unlikely to be driven entirely by the killings of assailants. Taken together, our findings raise serious doubts against the argument that Stand Your Ground laws make America safer.
My Comment Here: The MSM (media including FNC) don't find it newsworthy to report on miniority on minority violence. But alas, this is a 'Funded Study' so the numbers used at the raw data must represent every race, color and creed (said with just... a touch... of sarcasm). Read the Blog Comments. I also agree that the 'Seasonal Effect' skews the data and ..... (you be the judge).
... From a policy standpoint, I guess itís no surprise that Stand Your Ground laws could be associated with an increase in homicide. After all, these laws arenít really enacted as a homicide-control measure, right? Itís more the opposite, that they legalize certain violence that used to be criminal. I could imagine Stand Your Ground decreasing homicide in some sort of deterrence effect, but that would seem to me to be a bit of a bank-shot of an effect, hoping that legalizing some acts of violence would decrease others. Itís possible but I wouldnít bet on it. To put it another way, even if Stand Your Ground laws really did increase homicides, I could imagine people still supporting the laws on the grounds that some of these homicides were justifiable. I suppose that would be the next stage of research but it would take a lot more effort as it would have to investigate the story of each homicide.
post hoc, ergo propter hoc?
OK, a couple of points: "Significant" in this context means statistically significant - that is, probably (at least 95% sure) the differences are NOT due to chance variation. It does not mean significant in the social sense.
Second, If you look at the FBI data Bureau of Justice Statistics Homicide trends in the U.S.: Justifiable Homicides the number of justifiable homicides has been going down as a trend and the number by Police has always been greater than those by citizens - at least up to 2005.
The question is up or down compared to what?
For example: Romneycare in Mass. was predicted to increase the number of patients seen in Emergency Departments and if you compared the number seen after the law was passed with the number seen before, the number of patients did, in fact, go up. However, and this is important, if you compared the number with changes in neighboring states that DID NOT have Romneycare, they went up over the same time period as well, and by the same amount. The first argument is called 'post hoc, ergo propter hoc' - after the fact, therefore because of the fact - reasoning and is VERY dangerous in statistical studies (whole books have been written on measuring change).
I couldn't get a copy of the original paper so I really can't tell how the study was designed and I'm willing to bet that the people who picked up the abstract and reported the findings in the media a) didn't read it either and b) aren't qualified by training or experience to evaluate it either.
More recent data that I've seen but can't find the reference to suggests that since 2005, the number of justifiable homicides has gone up among both citizens and police. That might be due to SYG or (esp in the case of police) something else entirely.
I think it would be wise not to take this report too seriously until you have a chance to examine the data and methods.