Market Power, Labor's Share of Income, and Measured Productivity

For a long time, I have been making the argument that part of the reason for the inequality problem is distortions in the distribution of income driven by market imperfections such as monopoly power that allows prices to exceed marginal costs. What I didn't realize is that this can also affect measurements of productivity growth:

The relationship between U.S. productivity growth and the decline in the labor share of national income, by Nick Bunker: One of the ongoing debates about the state of the U.S. economy is the extent to which the profits from productivity gains are increasingly going to the owners of capital instead of wage earners. These researchers are debating the extent to which the labor share of income, once considered a constant by economists, is on the decline.

But what if the decline of national income going to labor actually affects the measured rate of U.S. productivity growth? In a blog post published last week, University of Houston economist Dietz Vollrath sketches out a model showing just that scenario. ...

Vollrath argues that businesses with more market power are able to charge higher markups on their goods and services, meaning their pricing is higher than the cost of producing an additional goods or services compared to pricing in a perfectly competitive market. So in this situation where markups are high, goods and services are being produced less efficiently, with the increased profits going to the owners of capital.

Vollrath argues that this is how measured productivity growth is affected by the decline of the labor share of income. Market power is important for thinking about measured productivity growth because, as Vollrath says, it “dictates how efficiently we use our inputs.” ... Impeding the most efficient use of capital and labor via marked-up prices will reduce measured productivity. ... Perhaps this could explain some of the reason why measured productivity growth looks so meager in the seeming age of innovation...

But Vollrath’s story isn’t a complete explanation of the fall in measured productivity, as he acknowledges...

But Vollrath’s market power explanation for falling productivity growth, alongside the falling share of national income going to wage earners, is supported by some evidence.  Work by Massachusetts Institute of Technology graduate student Matt Rognlie, for example, found evidence of higher markups.

Whether and how the decline of the labor share of income affects productivity growth is obviously a topic far too large for a couple of blog posts. But Vollrath’s model is especially interesting for connecting two important trends in recent years: the slowdown in productivity growth and the declining labor share. It’s worth, at the very least, a bit more investigation.