More Stand-Your-Ground, More Murder
June 14, 2012 11:29 AM Subscribe
posted by scunning (40 comments total)
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In addition to removing the duty to retreat when outside the home, Florida's 2005 "Stand Your Ground" law removed the civil liability to offenders who had acted within the law and added a presumption of reasonable belief of imminent harm necessitating a lethal response. These three elements were present in over 20 other state laws similar to Florida's. The following NBER working paper
by two Texas A&M economists provides new statistical evidence that these laws caused a 7 to 9 percent increase in homicides and non-negligent manslaughter. Consider this post a companion to this previously
, as well as this previously
"Since Florida adopted the first castle doctrine law in 2005, more than 20 other states have passed similar self-defense laws that justify the use of deadly force in a wider set of circumstances. Elements of these laws include removing the duty to retreat in places outside of one’s home, adding a presumption of reasonable belief of imminent harm necessitating a lethal response, and removing civil liability for those acting under the law. This paper examines whether aiding self-defense in this way deters crime or, alternatively, escalates violence. To do so, we apply a difference-in-differences research design by exploiting the within-state variation in law adoption. We find no evidence of deterrence; burglary, robbery, and aggravated assault are unaffected by the laws. On the other hand, we find that murder and non-negligent manslaughter are increased by 7 to 9 percent. This could represent either increased use of lethal force in self-defense situations, or the escalation of violence in otherwise non-lethal situations. Regardless, the results indicate that a primary consequence of strengthening self-defense law is increased homicide."
Media coverage at Business Insider
, Media Matters
, and Dallas Observer
For those interested in the statistical methodology used, it's called a form of multivariate regression analysis commonly called "differences in differences"
. Imbens and Wooldridge NBER lecture notes
are useful (slides
). Emmanuel Saez's lecture notes
are also nice if you want to compare. The theory of causality that diff-in-diff (or DiD, or DD) ascribes to is often called the Rubin-Neyman causal model
, or sometimes just the potential outcomes model
where causality is measured as the difference between the "actual outcome" and the "potential outcome" for a given unit with and without treatment, respectively.