Summary and Conclusions 149 



activity of industry and of the volume of trade, and at 

 an interval of about four years in the cycles of prices. 

 These conclusions brought to a close the last part of 

 our general problem of the cause and law of Economic 

 Cycles. 



The links in the sequence of causation were com- 

 pletely established: The fundamental, persistent cause 

 of the cycles in the yield of the crops is the cyclical 

 movement in the weather conditions represented by the 

 rhythmically changing amount of rainfall; the cyclical 

 movement in the yield of the crops is the fundamental, 

 persistent cause of Economic Cycles. 



In the Introduction to this Essay it was observed that 

 economic dynamics stands in need of a law that shall 

 be to a changing society what the law of diminishing 

 returns is to a society in a relatively static state. We 

 may now formulate the law: The weather conditions 

 represented by the rainfall in the central part of the 

 United States, and probably in other continental areas, 

 pass through cycles of approximately thirty-three years 

 and eight years in duration, causing like cycles in the 

 yield per acre of the crops; these cycles of crops con- 

 stitute the natural, material current which drags upon 

 its surface the lagging, rhythmically changing values 

 and prices with which the economist is more immedi- 

 ately concerned. 



