Experimental Pricing As an Approach to Demand Analysis 7

could be related to the time element. Prices of closely related
products, which, incidentally, changed simultaneously and uni-
formly in all stores, were included in this category. In addition,
this class contained other factors (temperature, holidays, pay-
days, etc.) that varied with time and which, very likely, affected
the demand for concentrate. The exceptional case-assumed
to be a function of time-related to the influence of price "age,"
i.e., the length of time a particular price for concentrate was
in effect, on the demand for concentrate. Presumably, by use
of this measure, a distinction could be drawn between ultra-
short-run and short-run demand curves. It was assumed that
price "age" could affect demand by shifting the demand curve,
changing the slope of the curve or both.
 No practical means was available for holding real income con-
stant along the demand curve. However, since expenditures for
orange concentrate represent only a minute fraction of the total


 Price D




 \ P3


 Sp1




 Sp2

 D'

 Quantity

 S = Supply at pth price (p = 0, ...4)