Gun ownership across countries

From the Economist magazine:

AN ESTIMATED 875m small arms are in circulation worldwide: one for every seven people on the planet. Nearly three-quarters of these are owned by civilians. And about 80% of those guns in civilian hands are found in just 30 countries, according to the Small Arms Survey, a research group. Although America accounts for 40% of firearms in civilian ownership, people put them to more deadly use elsewhere. The gun murder rate in Colombia and South Africa, for example, is much higher than in America. . . .

I am not sure where this 40 percent claim comes from.

Thanks to Harry Atkins for sending me this link.