In The Wall Street Journal Phil Gramm and Michael Solon write How to Distort Income Inequality- The Piketty-Saez data ignore changes in tax law and fail to count noncash compensation and Social Security benefits.
Messrs. Piketty and Saez also did not take into consideration the effect that tax policies have on how people report their incomes. This leads to major distortions. The bipartisan tax reform of 1986 lowered the highest personal tax rate to 28% from 50%, but the top corporate-tax rate was reduced only to 34%. There was, therefore, an incentive to restructure businesses from C-Corps to subchapter S corporations, limited-liability corporations, partnerships and proprietorships, where the same income would now be taxed only once at a lower, personal rate. As businesses restructured, what had been corporate income poured into personal income-tax receipts.
So Messrs. Piketty and Saez report a 44% increase in the income earned by the top 1% in 1987 and 1988—though this change reflected how income was taxed, not how income had grown. This change in the structure of American businesses alone accounts for roughly one-third of what they portray as the growth in the income share earned by the top 1% of earners over the entire 1979-2012 period.