Well, if you look at the British example, it's highly effective in enhancing sales of body armor:
A firm that supplies stab and bullet-proof vests to government agencies around the world said it had been flooded with orders following a series of brutal knife murders on Britain's streets.
VestGuard UK said it had received more than 100 calls from parents in London alone. It normally receives only one or two inquiries nationwide each year.
Some 60 jackets, costing between £300 and £425, have been sold - with parents saving up to buy the armour.
Shaun Ward, the sales director at VestGuard UK, said: "They are concerned by what is happening on the streets - the level of violence. A 13-year-old girl has been our youngest customer but most are about 15 or 16.
"We have a factory in Bolton and since Christmas we have been making really small vests that have a 28" chest and weigh 800 grams. The children have been mostly boys, but there are a few girls."
David Davis, the Shadow Home Secretary, said: "The fact parents are having to resort to spending large amounts of money on such drastic measures betrays the Government's failure to get a grip on violent crime.
"This is a consequence of having very little police presence on our streets and in our communities to detect and deter violent crime. While our police are tied up in red tape innocent children are having to wear police equipment to protect themselves."
Having conquered the problem of guns, why don't they just ban those 'Saturday Night Special' knives? You know, those long ones whose only real purpose is to kill people.