This information comes from a report by the Center for Disease Control and Prevention. I can't find the report itself, but it is referenced here:

http://www.pbs.org/newshour/bb/health-jan-june13-suicide_05-...

Edit - I found the report moments after posting that link. Here it is:

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6217a1.htm?mobile...