Assume that in the market for minority employees, an
unprejudiced employer will employ up to the point where the wage is equal to the
maginal productivity of a unit of labour.
Assume also that a
prejudiced employer will demand extra output ($D) on top of the wage inorder to compensate for his/her taste in discrimination. Thus the prejudiced employer will employ upto the point where the wage is $D below the
marginal productivity of a unit of labour.
Thus the unprejudiced employer will employ up to
efficient level of minority employees while the prejudiced employer will employ less than the
optimum level of minority employees.
This implies that an unprejudiced employer will maximise his surplus while the prejudiced employer will not. In the long run, the prejudiced employers will be bought out by unprejudiced employers as unprejudiced employers are able to earn higher
profits.
Alternatively, we can assume that corporations are employers. And the share-holders, in their drive to maximise their profit and therefore return, will vote out any manager who is prejudiced and discrimitory against a particular minority group.
Therefore in an
efficient market, employer prejudice will be driven out. Only unprejudice employers will survive.