122 Economic Cycles: Their Law and Cause 



at 187 1. 1 These two equations make it possible to 

 eliminate the secular trends upon which move the 

 cycles of prices and the cycles of yield. The results of 

 the calculations are given in Table VII of the Appendix 

 to this chapter. 



Figure 26 presents the cycles of yield per acre and the 

 cycles of general prices after the secular trends upon 

 which they were respectively superposed have been 

 eliminated. It is quite evident, now, from the appear- 

 ance of the graphs, that the cycles of yield per acre and 

 the cycles of general prices are closely related, and that 

 the cycles of prices lag several years behind the cycles of 

 crops. What is the amount of the lag and how closely 

 are the cycles correlated? Both of these questions may 

 be answered at once by following the method that was 

 adopted to measure the lag in the cycles of pig-iron 

 production. If the cycles of the yield per acre are 

 correlated 2 with the cycles of general prices we find, for 

 a lag of three years in general prices, r = .786 ; for a lag 

 of four years, r = .800; for a lag of five years, r = .710. 

 The cycles in the yield per acre of the crops are, there- 

 fore, intimately connected with the cycles of general 

 prices, and the lag in the cycles of general prices is 

 approximately four years. 



Figure 27 presents the two series of cycles with the 

 lag of four years in the cycles of prices eliminated. It is 



1 The first equation was computed from the data for 1875-1910, 

 and the second equation, from the data for 1871-1906. 



2 The data for the calculation are given in columns 4 and 7 of 

 Table VII in the Appendix to this chapter. 



