Under perfectly competitive conditions, the total output of an enterprise, valued at market prices, would reflect accurately the total returns from employing productive resources in a line of activity. In equilibrium, the opportunity cost of the factors employed at the margin of any line of activity would equal the returns, thus delimiting the possibilities for productive investment in that application. If similar conditions prevailed in every other productive application, there would be no further possibility-by allocating a little more of society's resources for producing more of one good and a little less for another-that any individual's gains would be more than sufficient to compensate the loss incurred by others.