I consider myself an armchair economist so what I am about to say might be missing something but I will summarize what I understand to be two sides to an issue.
We know that wages or income have been largely stagnant for most Americans since the mid-1970s. That is, when we take the incomes of Americans 40 years ago and adjust it for inflation, there has not been any improvement. There are a number of things to account for in this statistic and while I can't go into the reasons here, I will say that generally I believe it is true; despite an increase in productivity and increases in GDP since 1975, the average worker is not bringing home more money today than 40 years ago. (I say 'he' because it appears that the glass ceiling notwithstanding, women's income has risen on average since then. But of course the gender pay gap is still quite common and unfairness in pay between the sexes has not been adequately dealt with.)