Generating Cycles of Products and Prices 19 



according to the estimate ^ of the Secretary of Agricul- 

 ture, $15,873,000,000, and of this aggregate amount 

 the above six products contributed $11,238,536,000. 

 The records of the yields and prices of these six crops 

 from 1882 give the statistical material of which use is 

 made in the subsequent investigation. 



As the American production in case of all six of these 

 conmiodities is only a part of the world supply, our 

 first inquiry will be whether, notwithstanding this 

 fact, the domestic prices are inmiediately related to the 

 domestic yield. Furthermore, as we wish to eliminate 

 the varying factor of changing acreage, our inquiry will 

 take the fonn of ascertaining whether the domestic 

 prices of these several crops are immediately related 

 to the respective yields per acre. 



In order to secure a certain degree of comparability 

 in the graphs, the raw figures - of yield and the corre- 

 sponding December fann price were, for each crop, 

 converted into index numbers in which the average 

 yield and the average price for the years 1890-99 were 

 taken as the respective bases. The graphs of these index 

 numbers of yield and prices are given in Figures 4, 5, 6. 

 In each of the six graphs of yield and the six graphs of 

 prices the statistics show a secular trend which must be 

 ascertained as a preliminary to the work of finding the 

 relation between the variations in jdeld and the varia- 

 tions in prices. In each of the twelve curves the secular 

 trend was obtained by fitting a curve of the type 



y = a+hx-{- cx~ + dx^ 



^ Yearbook of the Department of Agriculture, 1919, p. 17. 

 ^ The raw figures of yield per acre and December farm prices were 

 taken from the Yearbooks of the Department of Agriculture. 



