Piketty and Marginal Productivity Theory

This paper focuses on Piketty’s explanation of the increased capital share of total income in major economies in recent decades presented in chapter 6 of his 2014 book. Piketty’s explanation is presented in terms of the theoretical framework of the marginal productivity theory of distribution. The first section of the paper critically reviews the key elements of marginal productivity theory: production function, marginal products, diminishing returns, and elasticity of substitution. The second section summarizes Piketty’s explanation of the increasing capital share in terms of marginal productivity theory; the third section critically evaluates Piketty’s explanation; and the fourth section briefly presents an alternative heterodox explanation of the increased capital share in recent decades.