The minimum wage is 23 percent less than its peak inflation-adjusted value in 1968. This is despite productivity (how much output can be produced in an average hour of work in the economy) more than doubling in that time period. The low-wage workforce has surely contributed to this rise in economy-wide productivity, since as a group they have far more education now than they did then. For the workforce overall, 37 percent in 1968 had not completed high school (or received a GED), which was true for only 9 percent in 2012 (the latest year with comparable data). We can drill down to examine low-wage workers, which we are defining for this analysis as those earning in the bottom fifth of the wage distribution.
“Low-Wage Workers Have Far More Education than They Did in 1968, Yet They Make Far Less,” Lawrence Mishel, January 23, 2014, Economic Policy Institute
As it turns out, unless you have policy people making sure that wages keep going up, policy people will make sure that they keep going down, even if you are more educated.