6 



Generating Economic Cycles 



the given data, and this may be ascertained by finding 

 the ampHtudes of trial cycles with periods between 

 limits that will be determined by the problem" in 

 hand. 



Suppose, for example, we wished to know what cycle 

 with period between three and twelve years would give 



Figure 2 

 The periodogram of annual rainfall in the Ohio Valley, 1839-1910. 



the largest amplitude in the annual rainfall of the Ohio 

 Valley for the interval of seventy- two years from 1839 

 to 1910. The results of the computation according 

 to the method that has just been sketched are graphed 

 in Figure 2. On the horizontal line the lengths of the 

 various trial periods are measured, and on the corre- 

 sponding perpendicular lines are plotted the squares of 



