If G' measures the return collected by employees, the total return, G", would be the sum of C and C'. In full equilibrium the total return would equal total costs,'or C" = C. Let a represent the fraction of the total return collected by firms. Since G = aG" and G" C, equation
(12) can be written as
MP'+aC—W+C, (13)
or
W = MP' — (1 — a)C.16 (14)
Employees pay the same fraction of costs, I — a, as they collect in returns, which generalizes the results obtained earlier. For if training were completely general, a = 0, and equation (14) reduces to equation
(10); if firms collected all the return from training, a 1, and (14) reduces
to MP0' = W0; and if 0 < a < 1, none of the earlier equations
is satisfactory.