In the first quarter of 2014, GDP in the U.S. plunged at a 2.9% annual rate, and productivity—the inflation-adjusted business output per hour worked—declined at a 3.5% annual rate. This is the worst productivity statistic since 1990. And productivity since 2005 has declined by more than 8% relative to its long-run trend. This means that business output is nearly $1 trillion less today than what it would be had productivity continued to grow at its average rate of about 2.5% per year.

Lagging productivity growth is an enormous...