32 
BULLETIN 1440, U. S. DEPARTMENT OF AGRICULTURE 
rur 
dots, one dot to each period, and knowing the accompany v r values 
of other factors which reflect the different things with Jhich the 
shape of the surface is expected to vary, the shape of the whole sur- 
face is measured by the solution of the mathematical equations which 
give data for computing its most probable position at any moment, 
under the assumptions implicit in the equations used. 13 
ILLUSTRATION OF THE SHIFTING RELATION OF SUPPLY TO PRICE 
Fig. 25.— The change in the demand for pork, 1907 to 1914. This shows the upward shifting of 
the demand schedule and also the change in the shape of the curve as demand increased 
The preceding discussion presents the basic assumptions upon which 
the subsequent analysis is based. Not all apply in every case, and 
some of the solutions use additional assumptions, which are at least 
implied in the discussion even if not explicitly stated. The specific 
conclusions to be drawn from the results of these analyses may vary 
as the viewpoint of the particular person doing the explaining varies. 
13 For a nonmathematical discussion of the assumptions which the statistical analysis itself involves, 
see the first part of the following: Ezekiel, M., a statistical examination of factors related to 
lamb prices. Jour. Pol. Econ. [now in press]. 
