Look back over the last hundred years and you’ll see the pattern. During periods when the very rich took home a much smaller proportion of total income — as in the Great Prosperity between 1947 and 1977 — the nation as a whole grew faster and median wages surged. We created a virtuous cycle in which an ever growing middle class had the ability to consume more goods and services, which created more and better jobs, thereby stoking demand. The rising tide did in fact lift all boats.
During periods when the very rich took home a larger proportion — as between 1918 and 1933, and in the Great Regression from 1981 to the present day — growth slowed, median wages stagnated and we suffered giant downturns.
Reich has been saying this for a while, now. Most of this editorial comes from his book Aftershock, which I reviewed last year. It's one of those rare economic books that keeps getting more relevant as time goes on. I highly recommend it.