The Small Arms Survey 2003 by the Graduate Institute of International Studies in Geneva found an estimated 238 million to 276 million private firearms in the United States, or roughly 83 to 96 guns per 100 people.

In comparison, there were 84 million firearms in the 15 countries of the European Union, 80 percent in private hands.

"Citizens of most European countries are more heavily armed than they realize, with an average of 17.4 guns per 100 people in the 15 EU countries alone," said Aaron Karp, a co-author of the study.

WAR.WIRE