US GDP has more than tripled from 1960 to 2011
1960 to 2011, the United States' Gross National Product has more than tripled from, growing from $521 Billion to $15 Trillion.
Source: U.S. Department of Commerce, Bureau of Economic Analysis, National Data: National Income and Product Accounts Tables: Table 1.1.5. Gross Domestic Product, http://www.bea.gov/iTable/iTable.cfm?ReqID=9&step=1#reqid=9&step=3&isuri... accessed March 18, 2013 [verified 4/17/14