 MRPL is the product of marginal revenue and the marginal product of labor or MRPL = MR × MPL.In the aftermath of the marginal revolution in economics, a number of economists including John Bates Clark and Thomas Nixon Carver sought to derive an ethical theory of income distribution based on the idea that workers were morally entitled to receive a wage exactly equal to their marginal product.In the 20th century, marginal productivity ethics found few supporters among economists, being criticised not only by egalitarians but by economists associated with the Chicago school such as Frank Knight (in "The Ethics of Competition") and the Austrian School, such as Leland Yeager.