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Published online by Cambridge University Press: 28 April 2015
The mechanization of American agriculture has played a key role in the technological progress of U.S. agriculture in this century (Heady and Tweeten). In turn, the demand for farm tractors and other farm machinery has been highly dependent on the year-to-year strength of the agricultural economy. Unit sales of tractors have varied by as much as 50 percent from one year to the next (Royal Commission on Farm Machinery).