The capitalist system moves in a never-ending cycle of booms and slumps. That has been the case for the last two hundred years. The cycle of booms and slumps, however, does not have a fixed and regular character. To begin with, the length of the cycle has always been somewhat flexible. In Marx's day it was an average of 10 years, but in the years of upswing after the second world war it was considerably less, something like 5-6 years, or even less. The exact length of the cycle is therefore not a principled question for Marxists. What is necessary is to analyse concretely the nature of the cycle, and try to establish how it will most likely evolve.