Scientism no doubt played a part in this. Jevons, who was explicit in his belief that economics should be like physical science, thought he could tie business cycles to the periodic change in sunspots. His mechanism operated via changes in agricultural output (believed to be correlated to sunspot changes via the weather) which, in turn, sparked change throughout the economy. Jevons believed he could demonstrate statistically that the periodicity of the sunspot was the same as that of the business cycle. Thus, economics, or at least a key part of the subject, could attain the predictive power of astronomy. Jevons may have carried connection of the cycle to calendar time further than anyone else, but business cycle theorists generally were entranced by the possible periodicity of the cycle with respect to the calendar. This notion withered gradually and is marked by the shift from the use of the word “cycle” to that of “fluctuation.” We should note that this emphasis on calendar time marked a clear separation from Marshallian microeconomics in which time, e.g., “the short-run,” was measured in purely economic terms without regard to the calendar.