144 Economic Cycles: Their Law and Cause 



were calculated. The equations to the law of demand 

 for all four crops conformed to a single type, indicating 

 that as the supply of the commodity increases, the price 

 falls. For reasons that were explained in the discussion, 

 we named this type of demand curve the negative type. 



It will be recalled that the three divisions of our 

 general problem were (1) the periodicity of rainfall; 

 (2) the effect of rainfall upon the crops; and (3) the 

 relation of the yield of the crops to Economic Cycles. 

 The elaboration of a method for calculating the demand 

 curves placed us in position to examine the third and 

 final part of the problem. The law of demand for the 

 crops connects the price of the several crops with their 

 respective supplies, but the supply is dependent upon 

 both the yield per acre and the extent of the acreage. 

 In order to bring our findings with regard to the period- 

 icity in the yield per acre into relation with prices and 

 values, it is clear that we must know the relation 

 between the variation in the price of the commodity 

 and the yield per acre of the commodity. This ques- 

 tion we examined at length, and found the tie between 

 price and yield per acre to be as close as the tie between 

 price and supply. To differentiate between demand 

 curves and curves showing the relation between yield 

 per acre and price, we called the latter curves, yield- 

 price curves. We deduced the equations to the yield- 

 price curves for the four representative commodities 

 and measured the degree of precision with which their 

 equations might be used as formulae for predicting 



