ELASTICITY OF SUPPLY AS A DETERMINANT OF DISTRIBUTION 93
marginal productivity of X would rise greatly above the amount
P; while that of Y would fall. But while this rise in the
marginal productivity of X to, let us say, P» would cause a
still further contraction in
the supply of X, the fall
in the productivity of Y
would cause an equal decrease
 in its quantity. The
differences in marginal
productivity would not,
therefore, be further accentuated
 from what they
were as the result of the
initial change in quantities
 arising from the expansion
 of production. An
equilibrium would result
in which the return to X
would be greater than P,
and that of Y would be less; and the amount of the differences
of the return of X and Y from P; would be greater than in Figure
9, where we assumed
elasticities of 0 and 1.0
respectively.
What would happen,
however, were the negative
 elasticity of X to be
greater than the positive
elasticity, namely —1.0
as compared with 4.5 as
is illustrated in Figure 12.
Then the initial increase
in effectiveness and in unit
return to each would cause
the supply of X to decrease
 twice as fast relatively
 as that of Y increased.
 Its marginal productivity would consequently rise
and that of Y would fall, but this would lead to twice as great
a relative decrease in the quantity of X as it would in that

y