Long-Run Changes in the U.S. Wage Structure: Narrowing, Widening, Polarizing. Lawrence Katz, Claudia Goldin, November 2007, Paper. “The U.S. wage structure evolved across the last century: narrowing from 1910 to 1950, fairly stable in the 1950s and 1960s, widening rapidly during the 1980s, and “polarizing” since the late 1980s. We document the spectacular rise of U.S. wage inequality after 1980 and place recent changes into a century-long historical perspective to understand the sources of change. The majority of the increase in wage inequality since 1980 can be accounted for by rising educational wage differentials, just as a…” Link