The current financial crisis was precipitated by a bubble in the US housing market. In some ways it resembles other crises that have occurred since the end of the second world war at intervals ranging from four to 10 years.
However, there is a profound difference: the current crisis marks the end of an era of credit expansion based on the dollar as the international reserve currency. The periodic crises were part of a larger boom-bust process. The current crisis is the culmination of a super-boom that has lasted for more than 60 years.