That's in the states.

Find me evidence that a society that was not previously armed, like ours, introduced guns and the crime went down.

It happens sometimes in London. How many people actually die though? After all, any one can buy a shotgun and hold up a place. We still posses the legal right to own a shotgun in this country, do you have one to defend your home with? Do you shoot regularly? Do you own a .22 rimfire and use it?