Generating Cycles in a Century of Prices 61 



we have found that in the yield per acre of the leading 

 crops in the United States, in the United Kingdom, 

 and in France, there are cycles of approximately 

 eight years, and these eight-year cycles in the three 

 countries are synchronous. We have also found that 

 the prices of the crops in the United States are closely 

 correlated with the yield per acre, the coefficients 

 of correlation ranging from r = — .2 to r = — .9 and 

 averaging r = — .7. 



It would, therefore, seem legitimate to assmne that if 

 there were cycles in the price of wheat in England 

 from 1760 to 1875, during a large part of which time 

 the importation of grain was restricted in consequence 

 either of wars or of corn laws, then there were cycles of 

 like period and opposite phase in the yield per acre of 

 the crops. 



If we compute a sine curve with a period of eight 

 years for the Poynting smoothed index numbers of the 

 price of wheat, which are given in Table IV, we find 

 (Figure 16) that 



(1) The curve fits the observations surprisingly 

 well throughout the 116 years of the record ex- 

 cept for the interval of the wars of the French 

 Revolution and the Napoleonic wars; 



(2) The eight-year cycle in the price of wheat, in 

 consequence of the law of demand, reveals an 

 eight-year cycle in the yield per acre of wheat 

 continuous with the eight-year cycle already es- 

 tablished for the crops of the United Kingdom ^ 



1 The data and original graph for the period 1884 to 1914 may be 

 found in the Journal of the Royal Slatisiical Society, May, 1919, pp. 

 384, 387. 



