Note: In each regression, observations are percentiles.  For log occupation wages and log employment shares, they are occupation percentiles.  For log wages, they are percentiles in the overall wage distribution.  For the first-column regressions, if occupations are used as observations instead of occupation percentiles, the R-squared values are the following:  0.029 for the 1979–1989 period with 260 observations, 0.041 for the 1989–2000 period with 326 observations, and 0.031 for the 2000–2007 period with 323 observations.  (The number of observations varies across periods due to the occupation coding changes discussed in the text and in the appendix.)  Thus, the result that very little of the variation in log occupation wages can be explained by changes in occupational employment shares is robust to using either occupations or occupation percentiles as observations.