I am deeply saddened by the recent mass-murder at Virginia Tech. One common feature of mass-murders of this nature is the use of guns. But why are guns the weapon of choice of mass murderers? Let's apply a little economics terminology to common sense, and see if we can figure it out.
The foundation of eonomics is rational behaviour. Given an objective function, economic agents do the best that they can, subject to the constraints that they face. Generally in economics we don't question where that objective function comes from. In this case, I'm glad.... I can't for a second imagine why some individual would want to kill as many people as possible (you might be glad to know!). But let's take that objective function as given, and move on....
Given the objective function, the constraints faced by the potential killer will determine how they carry out their plans. Clearly getting caught before carrying out your plan defeats the purpose. Therefore you need to choose a method that does not draw attention to your plans. In the United States, obtaining a gun by legal means is relatively easy, and as a result, there is also a large secondary market in handguns. Notice that in the latest tradgedy, the killer simply walked into a gun store and asked to buy a handgun. This was perfectly legal, and drew no attention from law enforcement. (Compare that to Hong Kong: if you wanted to obtain a handgun here, it would be very difficult, given the very low number of guns in circulation, and it is possible that you would end up getting arrested in the process).
Another constraint for the person intent on mass-murder is minimizing the marginal cost of additional deaths. With a gun, the marginal cost is a few cents for a bullet and a quick pull on a trigger. It's hard to imagine how the marginal cost of death could be lower! Again, a comparison with Hong Kong is informative. Here criminals generally "chop" their victims (with a meat cleaver) rather than shoot them. Without dwelling on the details, I think it would take a superb athlete to swing a meat cleaver with sufficient ferocity to kill 30 victims without them either running away or turning on him and disarming him. In short, the marginal cost of death is higher, and so the incidence of massacre is lower.
There are other costs too. A recent news story reported on a criminal who had hidden a 'chopper' in his trousers and had tripped over. He severed an artery, and bled to death. I suspect guns are less likely to inadvertedly turn on their ownes like that!
One response to such a massacre in the US which is a puzzle to most non-American is the response of the pro-gun lobb. They argue that the reason for the massacre is not that there are too many guns, but rather that there are too few! I am as puzzled as the next person by this strange idea, but since it is sometimes made by otherwise intelligent, educated, thoughtful individuals, what could they mean?
The arguments seems to be that if the students cowering under their desks had a handgun in their bag, they might have been able to return fire and take out the gunman. Under normal circumstances, the possibility that your victims might be armed might also reduce the prospect of such crime in the first place. There may be some merit to these arguments. If there is, it suggests two equilibria in the marketplace for gun ownership:
1) most people have guns; murder rates are low, because criminals are scared of being shot by their intended victims
2) there are few or no guns; murder rates are low because criminals lack a low-lost, low-risk means to kill
If we were to buy this dichotomy, then the US is in the unfortunate position of being somewhere between 1) and 2); maybe either more or less guns would be an improvement on their current state of affairs. To maintain the current non-equilibrium, expect more calls for increased campus security, and maybe even metal detectors at university campuses to try to stop guns from getting in, as is now the case at many high schools in the US.
However, even if equilibrium 1) really exists, I'd far rather live in equilibrium 2), as we do here in Hong Kong. It's easier to run from a meat-cleaver than a bullet!