All capitalist economies experience fluctuations in employment and economic activity around a long term growth rate. This book provides an explanation for this cyclical pattern of growth. The author considers whether the causes of fluctuations in output and employment are to be found outside the system or within it, and whether the long term growth rate corresponds to the growth of the labor force. Important Marxian and Keynesian insights into the growth process are confirmed within a rigorous framework of analysis that does not exclude the traditional neoclassical mechanisms.