Earlier quoted context omitted.
A fairly simple explanation that for some reason I don't see a lot of is the drop in union membership density around this time period. Such a drop would decrease bargaining power and therefore decrease the rate of wage increase
Is there a chart for that?
You can see union membership was on the decline since the 1950s, but it accelerated around the 70s. It is hard to see the timeline in that graph, in this one it is harder to see the acceleration, but it is easier to see the timeline: https://rpubs.com/jncohen/uniondensity