Greg Mankiw is the Chairman of Harvard's Economics Department. He also was the Chairman of George Bush's Council of Economic Advisers. He has also written a widely used macroeconomics textbook. His text attempts to explain the distribution of income in terms of marginal productivity theory. The share of income going to wages has been relatively constant, and Mankiw argues that this confirms marginal productivity theory. This article provides an extensive critique of marginal productivity theory as an explanation for the distribution of income. Some readers may want to read the critique of marginal productivity theory. I have selected two graphs from the article which deal with the practical implications of the critique.