How many guns there are in the U.S.

International research has found that U.S. mass shootings cannot be explained by a violent culture, racial divisions or mental health, the N.Y. Times' Max Fisher and Josh Keller write in "The Interpreter" column.

It's simply the "astronomical number of guns."

• "The United States has 270 million guns and had 90 mass shooters from 1966 to 2012."
• "No other country has more than 46 million guns or 18 mass shooters" — the U.S. is way worse than the Philippines, Russia, China or India.
• Americans alone own 40% of all guns in the world, more than all civilians combined in 25 other countries.

Countries with the highest gun ownership rate, per a survey by the Graduate Institute of International and Development Studies in Geneva:

1. United States: 120.5 per 100 people
2. Yemen: 52.8 per 100 people
3. Montenegro: 39.1 per 100 people
4. Serbia: 39.1 per 100 people
5. Canada: 34.7 per 100 people
6. Uruguay: 34.7 per 100 people
7. Cyprus: 34.0 per 100 people
8. Finland: 32.4 per 100 people
9. Lebanon: 31.9 per 100 people
10. Iceland: 31.7 per 100 people

Japan and Indonesia, meanwhile, have fewer than 1 firearm per 100.

A back-to-school Saturday in America ...