From Senior Scholar James Galbraith’s review of Thomas Piketty’s much-discussed Capital in the Twenty-First Century:

Although Thomas Piketty, a professor at the Paris School of Economics, has written a massive book entitled Capital in the Twenty-First Century, he explicitly (and rather caustically) rejects the Marxist view. He is in some respects a skeptic of modern mainstream economics, but he sees capital (in principle) as an agglomeration of physical objects, in line with the neoclassical theory. And so he must face the question of how to count up capital-as-a-quantity.

His approach is in two parts. First, he conflates physical capital equipment with all forms of money-valued wealth, including land and housing, whether that wealth is in productive use or not. He excludes only what neoclassical economists call “human capital,” presumably because it can’t be bought and sold. Then he estimates the market value of that wealth. His measure of capital is not physical but financial.

This, I fear, is a source of terrible confusion. […]

Piketty wants to provide a theory relevant to growth, which requires physical capital as its input. And yet he deploys an empirical measure that is unrelated to productive physical capital and whose dollar value depends, in part, on the return on capital. Where does the rate of return come from? Piketty never says. He merely asserts that the return on capital has usually averaged a certain value, say 5 percent on land in the nineteenth century, and higher in the twentieth.

The basic neoclassical theory holds that the rate of return on capital depends on its (marginal) productivity. In that case, we must be thinking of physical capital—and this (again) appears to be Piketty’s view. But the effort to build a theory of physical capital with a technological rate-of-return collapsed long ago, under a withering challenge from critics based in Cambridge, England in the 1950s and 1960s, notably Joan Robinson, Piero Sraffa, and Luigi Pasinetti.

Read the rest at Dissent magazine.