104 Economic Cycles: Their Law and Cause 



of each of these crops, the mean yield per acre for the 

 years 1890-1899 is taken as a base, and the yield per 

 acre for each of the years 1870-1911 is expressed as a 

 ratio of the base, comparable indices for the crops dur- 

 ing the period of forty-two years will be obtained. In 

 order to combine the nine series of figures into a series 

 that shall be representative of the whole of agriculture, 

 the several series must be properly weighted. The 

 method of weighting that was adopted in this particular 

 case was to assign to each crop an importance propor- 

 tionate to its value as compared with the total value of 

 the nine crops in 1911. The several weights were: for 

 corn, 36; wheat, 12; oats, 9; barley, 3; rye, .7; buck- 

 wheat, .3; potatoes, 6; hay, 16; cotton, 17. The index 

 numbers are given in Table I of the Appendix to this 

 chapter. 



Before comparing the index number for the yield 

 per acre of the crops with the volume of producers' 

 goods, we must make sure that we are keeping close 

 to the results obtained from a detailed investigation 

 of our four representative crops. If an index number of 

 the four representative crops is constructed upon the 

 same principle as the index for the nine crops, how 

 closely would the indices be correlated? In computing 

 the index of the yield per acre of the four representa- 

 tive crops, the weights assigned were: for corn, 50; 

 hay, 28; oats, 15; potatoes, 7. The index is given in 



tainccl from Circular 32, Bureau of Statistics, U. S. Department of 

 Agriculture. The yield for 1911 was obtained from the Yearbook 

 of the Department of Agriculture, 1911. 



