Transformation problem
In 20th-century discussions of Karl Marx's economics, the transformation problem is the problem of finding a general rule by which to transform the "values" of commodities (based on their socially necessary labour content, according to his labour theory of value) into the "competitive prices" of the marketplace. This problem was first introduced by Marxist economist Conrad Schmidt and later dealt with by Marx in chapter 9 of the draft of volume 3 of Capital.