OK, but how does lack of social cohesion cause a drop in real wages? There are a few mechanisms I can think of, and probably multiple are operating, but one way is that an atomized electorate does not have the ability to resist changes in the law that are detrimental to their broad interests. Thus, you get massive pro-corporate/shareholder legal changes that create increased competition for labor.

What's changed is that when a businessman needs some work done, the first thing he is going to look at is if the job can be automated. The second is that he'll look for lower cost offshore labor, made possible by cheap shipping and telecommunications, but also free trade agreements. The third is that he'll look to hire a legal or illegal immigrant who will take a lower wage. The fourth is that he'll look to move from a northern state to a southern right to work state, made possible by Taft-Hartley and its successors, and pliable Southern legislatures, where he can hire non-union labor who will take a lower wage. With so much new competition for labor, much of it government created, it's not surprising that economic growth is not flowing to labor.