It's been a decade since I heard anybody well-informed claim in a seminar that the top 1% premium and the college premium were driven by similar factors…
Greg Mankiw Forgets to Offer Data for his Biggest Claim: Greg Mankiw’s paper in the Journal of Economic Perspectives’ symposium on the top one percent… claims… the doubling of the income share of the top one percent reflects the increased economic contributions, or productivity, of those in the top one percent…. Mankiw’s evidence for this is pretty thin…. First, he rests on the work of Claudia Goldin and Lawrence Katz (2008) book, The Race between Education and Technology, that skill biased technological change continually increases the demand for skilled labor” and concludes that “the story of rising inequality, therefore, is not primarily about politics and rent-seeking but rather about supply and demand.” Mankiw acknowledges, however, that “Goldin and Katz focus their work on the broad changes in inequality, not on the incomes of the top 1 percent in particular. But it is natural to suspect that similar forces are at work.” Mankiw then argues that the growth of top one percent income shares and the premium earned by skilled relative to unskilled workers that Goldin and Katz study “follow a similar U-shaped pattern.”
That’s not much evidence and, in any case, it’s not even true: the growth of top one percent incomes has not followed the same pattern as the wage premium of ‘skilled’ workers (meaning the wage premium earned by college graduates).
Look at the figure below, which shows the regression-adjusted (log) wage premium of college graduates (including those with advanced degrees) relative to non-college educated workers and the ratio of top one percent incomes (including capital gains) to the incomes of the bottom ninety percent. These are shown as an index, with 1979 set to be zero, because the data are on far different scales. The first thing to stand out is that the top one percent income advantage moves like the stock market, much like the pay of executives and financial professionals, rising rapidly in the late 1990s, crashing after the tech bubble burst and again in 2008 and recovering as the stock market does so. The graph doesn’t show the 1970s, but as Goldin and Katz (and, obviously, Richard Freeman) have shown, the college wage premium fell in the 1970s. The top one percent share did not fall in the 1970s. These are different phenomena. I have had many conversations about this with Larry Katz (who, as I mentioned, Mankiw references and who also happens to be Mankiw’s colleague at Harvard). Katz agrees that the top one percent and the bottom 99 percent dynamics are driven by different factors. Greg Mankiw should walk down the hall and talk to him about this!
It is also the case that labor economists (including Goldin and Katz) have long noted that the college wage premium flattened out in the mid-1990s: it grew nineteen points from 1979 to 1995, grew another four points by 2007 and grew an additional half a percentage point by 2011. That is, the college wage premium grew roughly a fourth as much in the last fifteen years as it had in the prior fifteen years. Did the top one percent income advantage follow the same pattern? Absolutely not! The top one percent income advantage grew as much between 1995 and 2011 (despite the financial crash) as it did between 1979 and 1995. The growth of the top one percent income advantage grew far more between 1995 and 2007, before the crash, than it did in the earlier period. That is probably a stronger suggestion of a different pattern. CEO compensation grew a lot in 2012, not surprisingly, along with a growing stock market, so I suspect the top one percent is on its way to reestablishing its 2007 income advantage. There is no reason to think the income gains of the top one percent reflect the same forces as those driving education wage differentials.