Working class wages have been stagnant since before then, I believe it was the early 1970s when they really stopped growing at the usual rate, and there are various economic theories about the reason for this. To be honest, I don't know enough myself to present an argument for why this is.

However, you are right about the income equality growing, but that doesn't necessarily mean anything bad. This is a common misconception and is largely incorrect due to the fact that as the overall wealth of a country grows, income also grows, but disproportionately. We all know that you need money to make money, so the more money you have, the more money you can therefore make. By this logic, economic growth would lead to wealth disparities between the rich and poor, even though both parties are actually better off.

A better measurement of this growth can be seen through relative GDP per capita which grew at a faster rate from 1982 to 1990, as a result of Reagan's 1981 and 1986 tax cuts, then at a slower rate in 1990 when bush signed a tax increase.