248 ECONOMIC ESSAYS IN HONOR OF JOHN BATES CLARK 
is assumed to be 6 per cent and is distributed over the first six 
months of holding the grain. In the case of corn, the shrinkage 
is very heavy and varies from month to month throughout the 
year," and it is estimated that for the first ten months it amounts 
to 18.2 per cent and that for the last two months its amount is 
negligible. It is assumed that cotton undergoes no shrinkage in 
storage. In all cases the rate of interest is assumed to be 6 per 
cent per year and is figured on the price of the commodity at the 
date when it is assumed to have been ready for the market, or, 
in other words, at the beginning of the storage period.” 
On the assumption that the movement of prices for ten years 
is an adequate basis for discussion, the grain prices have been 
secured by taking the ten year average of the monthly high and 
low selling prices on the Chicago market; and the price of cotton 
has been determined by taking the ten year average of the high 
and low selling prices for twenty-eight interior towns in the 
United States. No attempt is made to give the total amount of 
a commodity thrown on the market during a given month, but, 
in the case of grain, it is assumed that the relative amount can 
be determined by the amount put upon certain principal markets; 
namely, Chicago and Minneapolis in the case of wheat, and 
Chicago in the case of oats and corn, while for cotton the amount 
elivered at twenty-eight interior towns is taken. 
It is apparent that in a country as large as the United States 
all of a given commodity is not ready for the market at the same 
time, and the date on which the farmer may sell his crop must be 
more or less arbitrarily assumed; but if the movement throughout 
the year be kept in view, the date chosen as a basis for com- 
parisons cannot materially affect conclusions. The date taken for 
wheat and oats is August; for corn, December; and for cotton, 
November. The average price on these respective dates and 
the average amount put on the market then are taken as bases 
for computing the relative prices and amounts for the other 
months of the year. For example, the average ten year price of 
1 Tt is estimated that the shrinkage up to December is 6.9 per cent; 
January, 7.5 per cent; February, 7.8 per cent; March, 9.7 per cent; April, 
12.8 per cent; May, 14.7 per cent; June, 16.2 per cent; July, 17.3 per cent; 
August, 17.8 per cent; September, 18.2 per cent. (Unpublished monograph 
on the Marketing of Farm Products, Dr. H. W. Gilbertson.) 
® The price taken is the wholesale market price, and not the price 
received by the farmer. It is evident that this somewhat exaggerates the 
interest charge.