In the years following its publication, F.A. Hayek & rsquo; s pioneering work on business cycles was regarded as an important challenge to what was later known as Keynesian macroeconomics. Today, as debates rage on over the monetary origins of the current economic and financial crisis, economists are once again paying heed to Hayek & rsquo; s thoughts on the repercussions of excessive central bank interventions. The latest editions in the University of Chicago Press & rsquo; s ongoing series The Collected Works of F.A. Hayek, these volumes bring together Hayek & rsquo; s work on what causes periods.