The bottom line is that technological automation is rapidly displacing labor, and therefore those who own the means of production own a greater share of the profits. Stated another way, those who are already wealthy are seeing their wealth increase at an even faster rate due to automation.
There’s a great/controversial recent episode of This American Life (in partnership with Planet Money) which is, on the surface, about disability payments. However, I found the subtext to actually be about this increasing effect of automation on the economy, with “disability” payments actually serving as a crude transfer mechanism to alleviate some of the symptoms.
I’m not sure what’s going to happen, but I think there will have to be some major societal shift to deal with the problem.