I think the highest productivity increases have come in manufacturing. So, the way I read it is that those with "lower education levels," which is a euphemistic way of saying "working class," were much more productive than many of the comments care to admit. Also, what I find kind of amusing about the paper is that there are no actual social struggles in the history of this country. The paper mentions The Treaty of Detroit. But where did the UAW actually come from? On the other hand, when the paper mentions the decline of unions, it is blamed on "objective" factors, like trade. Did the author ever hear of PATCO? To sum up, I guess that we are supposed to think that working people are just "little people" with no education, who are not very productive, but instead are just passive pieces of jelly who are acted upon by the big brains who run the private and public sectors -- all under the watchful and enlightened eyes of our academic "consciences."