Summary and Conclusions 147 



Beyond what we had already established, this theory 

 of the interrelation of economic changes required for 

 its complete demonstration the proof of the existence of 

 two fundamental relations, to wit, that the cycles in the 

 yield per acre of the crops are reproduced 



(1) in the activity of general industry; 



(2) in the movement of general prices. 



In order to test whether these relations actually exist, 

 an index number of the yield per acre of the crops was 

 constructed for the nine crops, corn, wheat, oats, barley, 

 rye, buckwheat, hay, cotton, and potatoes. To make 

 sure of keeping close to the results already established 

 for the representative commodities corn, hay, oats, and 

 potatoes, the correlation of the index of the nine crops 

 with the index of the four representative crops was 

 computed and found to be r = .960. 



As the production of pig-iron is generally regarded as 

 a good "barometer" of the activity of industry, we 

 sought an answer to the above first question by in- 

 vestigating whether the cycles in the yield per acre of 

 the nine crops were reproduced in the cycles in the 

 production of pig-iron. The inquiry involved the 

 problems of the separation of the cyclical and the secular 

 movements in the production of pig-iron, and the 

 ascertainment of the amount of the lag in the cycles 

 of pig-iron behind the cycles in the yield per acre of the 

 crops. We found that it takes between one and two 

 years for the stimulation of increasing harvests to work 

 out its maximum effect in promoting the activity of 

 industry as that activity is represented in the "barom- 



