Check out the govt debt bubble. Or the debt bubble in general.
Global debt has grown by $57 trillion in seven years following the financial crisis | News | The Guardian
The US consumer has been paying theirs down for the last two years or whatever it is but that is nothing in the 15 year time line. Japan is basically screwed and no one wants to admit it.
Forget Greece, Japan is the world's real economic time bomb - Fortune
China has blown up their debt in every sector but honestly they save so much hard cash that I doubt it could be an issue except as a draw on growth at some point.