Summary and Conclusions 145 



prices. In all of these relations, the yield-price curves 

 were found to be as accurate and as satisfactory as 

 the demand curves themselves. 



With the possession of the yield-price curves, showing 

 the relation between the prices of the crops and their 

 varying yield per acre, it might seem that the problem 

 of agricultural cycles at least was completely elucidated. 

 As we know how the periodicity in the yield of the crops 

 follows upon the periodicity in the rainfall, and how the 

 prices vary with the yield, one might conclude that 

 the course of prices could be predicted for a long time. 

 The inference would be entirely true but for the fact 

 that the demand curves and the yield-price curves move 

 alternately up and down with the flow of time. This 

 complication made it necessary to investigate the 

 rhythmical movement of the yield-price curves, and 

 we found that the demand curves, or yield-price curves, 

 rise or fall with the level of general prices and with the 

 level of the index of the yield per acre of the crops. 



The preceding facts seemed to involve a contradiction 

 with an a priori doctrine of theoretical economics. 

 According to the economic dogma of the uniformity of 

 the demand function, all demand curves are of the 

 negative type: As the amount of the commodity in- 

 creases, the price falls. But if this be true, how is it 

 possible for a fall of general prices to accompany a fall 

 in the index of the yield per acre of the crops? If the 

 yield per acre of the crops decreases, then, according to 

 the yield-price curves and the demand curves, the price 

 of the crops will rise. Moreover, as the profits of trade 



