Economists don’t agree on much but they do tend to converge on one idea – productivity improvements are the key to long-term prosperity. Except that who benefits from productivity increases matters as much as the efficiency gains themselves, according to two reports from the liberal Economic Policy Institute in Washington.

The first finds that rising income inequality in the United States means that the benefits of better productivity are accruing mainly to the very wealthy. The EPI offers this startling nugget of data as basic food for thought: U.S. productivity grew 80.4 percent from 1973 to 2011, while average hourly compensation rose just 39.2 percent in the same period, and median compensation, which excludes outliers, gained a paltry 10.7 percent.

Writes Lawrence Mishel, EPI president and author of the reports:

Productivity growth, which is the growth of the output of goods and services per hour worked, provides the basis for the growth of living standards. However, the experience of the vast majority of workers in recent decades has been that productivity growth actually provides only the potential for rising living standards: Recent history, especially since 2000, has shown that wages and compensation for the typical worker and income growth for the typical family have lagged tremendously behind the nation’s fast productivity growth.

John Tasini, a labor activist who made an unsuccessful bid for the U.S. Senate in 2006, puts the disparity in perspective by calculating what the minimum wage would be if its rise had kept up with productivity growth, as it did before the mid-1970s.

The minimum wage today, if it reflected productivity gains over the last 30 years, should be between $19-$20 an hour. Raising the minimum wage, then, to $8.50 an hour seems like a big deal – except when you understand that it hides the vast robbery that has taken place of the past 30 years and it certainly will not make it possible for people to live with dignity and respect.