Two key things occurred during the time period you're talking about where wages stagnated in spite of massive increases in productivity growth. The first is th

Two key things occurred during the time period you're talking about where wages stagnated in spite of massive increases in productivity growth. The first is that we actually started letting women get jobs. We increased the labor supply by nearly 40%. It's amazing that wages are not even lower than they are. The second thing that happened is that millions upon millions of unskilled immigrants crossed the border. This also, obviously significantly increased the pool of labor at the bottom of the economic ladder further suppressing wages.