http://www.americanexperiment.org/uploaded/files/aeqv2n2lott.pdf The basic argument for those who don't want to read 11 pages of stuff: Suppose firearms were readily available and law abiding citizens yesterday all along street had firearms. They would have been able to then shoot Bird and disarm him after he shot his first victim - thus saving 11 lives. How much crime would actually be stopped if more people had firearms? Cities with high rates of gun ownership where you can buy a gun in Walmart in the USA have incredibly low levels of crime. People don't even lock their doors at night. Places like LA/Washington DC with tight gun control laws are among the worst affected in the US. There's actually an almost perfect inverse relationship between the rates of licensed gun ownership and the crime rates. Is this cause or effect? It's game theory at its purest - by creating a real threat you create a stable equilibrium.