The Mechanism of Cycles 99 



whole country should be considered. We need, how- 

 ever, to assure ourselves that, in taking this more 

 comprehensive view of the yield of crops, we have not 

 lost the characteristic cyclical movement of the yield 

 which we discovered in the more limited study. We 

 desire to know how closely the yield per acre of the 

 whole country is correlated with the yield per acre of 

 our representative state of Illinois. 



The correlations of the annual differences in the yield 

 per acre in Illinois and the annual differences in the 

 yield per acre in the United States were, in case of our 

 four typical crops, for corn, r = .855; for hay, r = .745; 

 for oats, r = .800; for potatoes, r = .843. The period 

 covered in all cases was from 1866 to 1912 inclusively. 

 The data were obtained from Bulletins, 56, 58, 62, 63 

 of the Bureau of Statistics of the United States Depart- 

 ment of Agriculture and from the recent Yearbooks of 

 the same Department. A reference to the Table given 

 a moment ago will show that the yield per acre of crops 

 in Illinois is at least as closely related to the yield per 

 acre of the same crops in the United States, as the prices 

 of the several crops are related either to the supply 

 of the crops or to the yield per acre of the crops. More- 

 over, the very high values of the coefficients leave but 

 little room for doubt that the cyclical movement of the 

 yield per acre in the Middle West is representative of 

 the movement of the crop yield in the whole of the 

 United States. 



