I have just come across an International Monetary Fund working paper on income polarization in the United States that makes an important contribution to the secular stagnation debate. The authors — Ali Alichi, Kory Kantenga and Juan Solé — use standard econometric techniques to estimate the impact of declines in middle class incomes on total consumer spending. They find that polarization has reduced consumer spending by more than 3 percent or about $400 billion annually. If these findings stand up to scrutiny, they deserve to have a policy impact.

This level of reduction in spending is huge. For example, it exceeds by a significant margin the impact in any year of the Obama stimulus program. Alone it would be enough to account for a significant reduction in neutral real interest rates. If consumers were spending 3 percent more, there would be scope to maintain full employment at interest rates much closer to normal. And there would be much less of a problem of monetary policy’s inability to respond to the next recession.

What is the policy implication? Principally, it is the macroeconomic importance of supporting middle class incomes. This can be done in a range of ways from promoting workers right to collectively bargain to raising spending on infrastructure to making the tax system more progressive. These are hardly new ideas. And I supported them before seeing this new research. But there is now another powerful argument in terms of mitigating secular stagnation in their favor.

Lawrence H. Summers, the Charles W. Eliot university professor at Harvard, is a former treasury secretary and director of the National Economic Council in the White House. He writes occasional posts on Wonkblog about issues of national and international economics and policymaking.