Same survey (maybe?) shows that U.S. gun owners on average own 4.4(ish) guns per owner. A quick search of the number of guns in the whole world gives me a wiki.answers.com reply of some 12 billion guns in the whole world (excluding .50 cal and above weapons) and wikipedia says the population of the world is around 7 billion. There are also surveys that show how gun ownership is at pre-1970s levels (at around 70ish/100 residents)