http://en.wikipedia.org/wiki/Kondratiev_wave

and wondering to what extent we are seeing credit financing the creation of new waves of technology to give the upswing followed by periods of repayment of the debt (and hence monetary contraction in a deficit-based monetary system) from the revenues from the new generation of productive assets, on the downswing.

So cycles - bounded by the mathematics of compound interest on the money supply - would be intrinsic to our current - deficit-based - form of Capitalism.

"The future is already here -- it's just not very evenly distributed" William Gibson