Even though this will make you mad, I’m going to go there anyway.
No, I have not gone over to the dark side. Relax. I’m not going to start spouting insane GOP talking points. I have not become an Austrian economist or a frothing libertarian.
But what I am, in my heart, is a scientist. I believe in data and going where the data lead. In the case of concealed-carry, I am merely reacting to the available data on the question and I find reasonably good evidence that there may be value in the law, or, at least no additional harm from the law. I hope you will come with me on this brief review of the epidemiological and criminological research with an open mind.
The data on concealed carry are mixed, but perhaps the most comprehensive review of the studies comes from a 2003 book published by The Brookings Institution entitled Evaluating Gun Policy: Effects on Crime and Violence. Chapter 8, The Impact of Concealed-Carry Laws (pdf) addresses the question head-on.
Those interested in a detailed look at the impact of concealed-carry should take the time to read the entire chapter, especially if they’re interested in an up-close-and-personal look at an abstract statistical debate between experts. I’m not going to dive into much detail here, just summarize their summaries and show you a chart which, to me, is fairly convincing and demonstrate that concealed-carry may be a good thing (or at least not a horrible thing).
The chapter is divided into three parts. Part 1 presents a statistical review of past literature which finds that concealed-carry is harmful. The second part is a response from the authors of the original study. The third part is a methodological and statistical review which is, quite frankly, over my head. Having read the chapter, and looked at the research, it’s my conclusion that the data tip the scales in favor of concealed-carry or, in a worst-case interpretation of the results, say that concealed-carry does no harm.
The evidence is reasonably convincing (to me) that concealed-carry laws likely reduce crime rates. I know that seems counter-intuitive, and it pains me to admit that the NRA might be right on this (or about anything, for that matter), but the data reveal a pattern of decreasing criminality following the passage of concealed-carry laws in 33 states. If we look at the impact of the entire period under study, from 1979 – 1997, we see the following result:
What you see here is a trend that, over time, after the concealed-carry law is passed, the incidents of murder and rape fall off dramatically as do assault an robbery decrease sometime later. There are several explanations posited for this, most of which rely on the fear of criminals from being shot by armed citizens. They likely shift their criminality to areas that are non-confrontational or are effectively deterred.
If you add to this the question of how much violent crime is added to a community by the holders of concealed-carry permits, you’ll find that these numbers are quite low. There is little evidence to support the theory that permit holders commit crimes violent crimes. In fact, their criminality is lower than the general population.
Finally, it is important to recognize that this effect is only seen in densely populated urban areas where crime is already high. There is little impact on rural crime rates (which are traditionally low).
Now the reason I find this idea somewhat convincing comes from the study of immunology. In immunology, there is what is known as the herd effect or herd immunity. The theory of herd immunity
describes a form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals who have not developed immunity. Herd immunity theory proposes that, in contagious diseases that are transmitted from individual to individual, chains of infection are likely to be disrupted when large numbers of a population are immune or less susceptible to the disease. The greater the proportion of individuals who are resistant, the smaller the probability that a susceptible individual will come into contact with an infectious individual.
If we think of crime as the the disease and concealed-carry as the immunity, herd immunity states that not everyone in the population needs to participate in concealed-carry for the entire population (the herd) to see a benefit. So if only 2% of the population is armed with concealed-carry, that might be sufficient to protect the whole population. It might even be that gun ownership rates drop as a result of the impact of concealed-carry on crime rates.
So in a densely populated, high crime area, the mere belief that more people are carrying concealed-weapons than actually are carrying may be enough to deter crime. Just the fear of an armed citizen might be enough for a criminal to think twice about committing a crime.
Can I prove that this herd immunity theory is correct in it’s application to concealed-carry? No. But it is a model which fits the data and as such, deserves consideration and further research.