10 BULLETIN 1411, U. S. DEPARTMENT OF AGRICULTURE 
required from the retailer. Practically as much of the storekeeper's 
or clerk's time is needed to wait upon a customer who purchases a 
small quantity of goods as for the person who makes a large purchase. 
It is a reasonable supposition, therefore, that the selling expense 
should be fairly uniform for each retail sale, irrespective of its size. 
SIZE OF SALE AS CRITERION OF SERVICE REQUIREMENTS 
Careful inquiries in the retail trade revealed the fact that the size 
of the average retail sale varies distinctly with different commodities. 
These specific inquiries embraced the extensive experience of two 
large metropolitan chain-store systems, several independent retailers, 
and a considerable number of individual families whose size of pur- 
chase were included with the original price data. 
Although retail prices are advertised in terms of" uniform physical 
units, such as the number, quart, head, dozen, or a similar magnitude, 
actual sales are made in various multiples of these individual units. 
To be sure, there is a great deal of variation in the size of individual 
sales on account of differences in buying habits of individual cus- 
tomers. Yet sufficient regularity exists throughout the retail trade 
to establish a typical or prevailing size of sale for a given commodity. 
In retail selling the significance of the variation in quantities of 
goods sold per sale lies in their relation to the money value of the 
goods so sold. The value of the retail sale is determined by two 
variable elements. One of these is the physical quantity of good:* 
disposed of; the other is the price per physical unit of goods. 
From the representative sources referred to, which may be con- 
sidered typical of retailing practices in the metropolitan area, it was 
possible to ascertain with considerable definiteness the prevailing 
range in size of sale for each commodity. The size of the typical 
or standard retail sale for each commodity may reasonably be re- 
garded as approximating the mid-point of the prevailing range. Use 
of the mid-point is justified as an approximate indicator of prevailing 
size of sale, in view of the fact that extremes, such as unusually small 
sales and unusually large sales, were excluded from the ranges given. 
This method involves some degree of approximation, but in the ab- 
sence of more definite data for arriving at specific accuracy, which 
could be obtained only by recording exact details of a large number 
of individual sales under representative conditions, the method 
here employed is justified as the best that was available. 
Retail price per unit of goods, which is the second variable in the 
value of the retail sale, was computed uniformly per pound, on the 
same basis as that used for expressing the size of sale. Retail price 
per pound was calculated from the mean retail price of each com- 
modity as derived from the original quotations. These were first 
converted to the package or hundredweight basis and thence to the 
mean price per pound. 
The value of the standard retail sale was calculated as the product 
of the mean retail price per pound and the number of pounds hi the 
standard retail sale. The prevailing range in size of sale for each of 
the 14 commodities, the mid-point of this range, and the value of the 
standard retail sale, are shown in the first three columns of Table 4. 
Spread between the wholesale cost of goods and their retail value 
may be computed either by subtracting the wholesale price of a given 
quantity from its retail price, or indirectly by multiplying a given 
