26 Generating Economic Cycles 



cycle is given in the lower part of Figure 8. This out- 

 come of the calculations* is gratifying because of its 

 consonance with results that have already been ob- 

 tained. Other investigations '^ have shown that there 

 are eight-year cycles with maxima approximately at 

 1882, 1890, 1898, 1906, 1914 in the annual rainfall of 

 the United States as a unit, in the annual rainfall of the 

 Ohio Valley, the May and June rainfall of the Dakotas, 

 and in the yield of wheat, oats, and barley in the Da- 

 kotas, the United States, the United Kingdom, and 

 France. 



The Derived Cycle of Prices 



An index number of the combined yield of the six 

 crops was devised, as we have just described, by simi- 

 ming the percentage deviations of the yields from their 

 respective secular trends. To carry the inquiry beyond 

 the stage that was reached in the last section an index 

 number of the combined prices of the six crops was con- 

 structed by summing, for each year, the percentage 

 deviations of the prices of the several crops from the 

 respective secular trends of prices. The data are given 

 in Table IV of the Appendix. These two index nmn- 

 bers — the index of the combined yield and the index of 

 the combined prices — supplied the material for the 

 next stage in the problem, namely, to ascertain the 

 degree of relation between the variations in the index 



1 "Forecasting the Crops of the Dakotas," Political Science Quarterly, 

 June, 1919, pp. 228, 229 "Crop Cycles in the United Kingdom and 

 in the United States," Journal of the Royal Statistical Society, May, 1919. 

 "Crop Cycles in the United Kingdom and in France," ibid.. May, 1920. 

 "An Eight- Year Rainfall Cycle," Monthly Weather Review, July, 1922. 



