Margin of Profit:
years ago, I was
living in a part of Manhattan near Columbia University. When I
necessary to go out at night I carried with me a four-foot
walking stick. My
friend Ernest Van den Haag argued that I was making a dangerous
potential muggers would see my behavior as a challenge and swarm
all over me. I
responded that muggers, like other rational businessmen, prefer
to obtain their
income at the lowest possible cost. By carrying a stick I was
not only raising
the cost I could inflict on them if I chose to resist, I was
also announcing my
intention of resisting. They would rationally choose easier
I never did get mugged, which is some evidence for my view. More comes from observing who does get mugged. If muggers are out to prove their machismo, they ought to pick on football players; there is not much glory in mugging little old ladies. If muggers are rational businessmen seeking revenue at the lowest possible cost, on the other hand, mugging little old ladies makes a lot of sense. Little old ladies—and other relatively defenseless people—get mugged. Football players do not. It is said that when someone asked Willie Sutton why he robbed banks his answer was that that's where the money is.
The economic approach to crime starts from one simple assumption: criminals are rational. A burglar burgles for the same reason I teach economics, because he finds it a more attractive profession than any other. The obvious conclusion is that the way to reduce burglary is by raising the costs of the burglar's profession or reducing its benefits.
The analysis that helped me decide what to take with me on my evening strolls around Manhattan's Upper West Side can also be applied to a point that comes up in arguments over gun control. Opponents argue that gun control, by disarming potential victims, makes it more difficult for them to protect themselves. Supporters reply that since criminals are more experienced in violence than victims, the odds in any armed confrontation are with the criminal. This is probably true, but it is almost entirely irrelevant to the argument.
Suppose one little old lady in ten carries a gun. Suppose that one in ten of those, if attacked by a mugger, succeeds in killing the mugger instead of being killed by him or shooting herself in the foot. On average, the mugger is much more likely to win the encounter than the little old lady. But, also on average, every hundred muggings produce one dead mugger. At those odds, mugging is an unprofitable business—not many little old ladies carry enough money to justify one chance in a hundred of being killed getting it. The number of muggers declines drastically not because they have all been killed but because they have, rationally, sought safer professions.
When, as children, we learn about different sorts of animals, we imagine them in a strict hierarchy, with the stronger and more ferocious preying on everything below them. That is not how it works. A lion could, no doubt, be fairly confident of defeating a leopard, or a wolf of killing a coyote. But a lion that made a habit of preying on leopards would not survive very long; a small chance of being killed and a substantial risk of being injured is too high a price for one dinner. That is why lions hunt zebras instead.
In analyzing conflict, whether between two animals, criminal and victim, competing firms, or warring nations, our natural tendency is to imagine an all-out battle in which all that matters is victory or defeat. That is rarely if ever the case. In the conflict between the mugger and the little old lady, the mugger, on average, wins. But the cost of the conflict is high enough so that the mugger prefers to avoid it. In this case as in many others, the problem faced by the potential victim is not how to defeat the aggressor but only how to make aggression unprofitable. The logic of the problem is nicely summed up in Van Rijn's reply to one of his colleagues who suggests that they should fight even if it costs more than the trade is worth to them:
"Revenge and destruction are un-Christian thoughts. Also, they will not pay very well, since it is hard to sell anything to a corpse. The problem is to find some means within our resources to make it unprofitable for Borthu to raid us. Not being stupid heads, they will then stop raiding and we can maybe later do business."
I made this point, using a little old lady with a pistol in her purse as my example, in an economics textbook published in 1986. Eleven years later John Lott and David Mustard published an article offering statistical evidence that laws allowing concealed carry tended to reduce crimes, such as rape or mugging, that required the criminal to confront his victim.  That set off a lively academic controversy, with statistical articles supporting and others contradicting Lott and Mustard’s result, and a parallel political controversy. The result of the latter is that ten states currently permit concealed carry without a permit and thirty-one have laws requiring the authorities to issue a concealed carry permit unless they have good reason to withold it. Whether the result is more crime or less is still a question that people disagree about, with the division largely along political lines.
Two men encountered a hungry bear. One turned to run. "It’s hopeless,” the other told him, “you can’t outrun a bear.” “No,” he replied "But I might be able to outrun you.”
 John R. Lott, Jr. and David B. Mustard, “Crime, Deterrence, and Right-to-Carry Concealed Handguns,” The Journal of Legal Studies, Vol. 26, No. 1 (January 1997), pp. 1-68.
 I followed the controversy for a while on my web page with the assistance of John Lott to point me at articles supporting his position and Tim Lambert, a critic of Lott’s argument, to point me at articles on the other side. Eventually the statistical arguments reached a level beyond my competence to evaluate. For my account of the early stages, see: http://www.daviddfriedman.com/Lott_v_Teret/Lott_Mustard_Controversy.html.