ARTHUR F. BURNS, National Bureau of Economic Research
Shortly before his death Wesley Mitchell put in my care the completed parts of the "progress report" he was preparing on his long and elaborate investigation of "what happens during business cycles". This book is substantially the document he left behind. I have felt free to make numerous changes of detail, but I have not interfered with the design, nor attempted to complete the narrative. The work of a major scientist, even if not half done, deserves a life of its own, unencumbered by the hand or voice of another. So it is especially when, as in the present case, the fragment has well defined contours, balance, and direction. But for the guidance of students who may take up the book for the first time, I shall put down a few remarks about Mitchell's objectives and what he accomplished.
Business cycles are not merely fluctuations in aggregate economic activity. The critical feature that distinguishes them from the commercial convulsions of earlier centuries or from the seasonal and other short-term variations of our own age is that the fluctuations are widely diffused over the economy -- its industry, its commercial dealings, and its tangles of finance. The economy of the western world is a system of closely interrelated parts. He who would understand business cycles must master the workings of an economic system organized largely in a network of free enterprises searching for profit. The problem of how business cycles come about is therefore inseparable from the problem of how a capitalist economy functions.
This conception governs Mitchell's posthumous book, as it does his____________________