This info graphic is very telling.  It is from the recent IMF forecast reported here:
http://www.marketwatch.com/story/imf-bombshell-age-of-america-about-to-end-2011-04-25?dist=countdown
It seems I’ve heard this before in history class.  The following excerpted from Wikipedia:
In The History of the Decline and Fall of the Roman Empire (1776–88), Edward Gibbon famously placed the blame on a loss of civic virtue among the [...]