In a nutshell: An economics expert writing in the South Bend Tribune argues that the supply of well-paying, low-skilled jobs that once sustained the American middle class has dried up, while educational attainment has stagnated.
Shift in the middle classThe United States has always had something like a middle class, but for most of our history it has been a distinction of class not necessarily dependent on income or wealth. In that sense we have been unusual among nations in allowing a Ben Franklin, Abe Lincoln or Harry Truman to do the same jobs as a Washington or Roosevelt.
via Southbendtribune