President Obama recently used his weekly radio address to insist that the United States can outcompete any other nation on earth if only we “unlock the productivity” of American workers. But the president’s advocacy of productivity—getting more or better value for each hour worked—as the key to competitiveness may fall on deaf ears in some quarters. Longstanding misconceptions continue to undermine rational debate on productivity. Here are a few of the most pervasive.

Productivity is not a priority. The United States relies more than ever on productivity gains to drive GDP growth. Productivity generated 80 percent of total GDP growth in recent years compared with 35 percent in the 1970s. Now, due to our country’s shifting demographics, we’ll have to do even better.

In the past, productivity gains and an expanding labor force made equal contributions to economic growth. But this is changing as baby boomers retire and the number of women entering the work force levels off. If labor-force growth slows as projected and productivity increases at the average 1.7 percent annual rate posted since 1960, annual GDP growth will fall to 2.2 percent from its historic average of 3.3 percent. Americans on average would experience slower gains in...