Why do leading estimates of top income shares differ so much?
Core argument: Piketty-Saez-Zucman report the top 1% income share rising from 9.1% to 15.6% between 1979 and 2015, while Auten-Gerald-Splinter find a smaller increase from 7.2% to 8.5% over the same period.
The debate between Auten/Gerald/Splinter (AS) and Saez/Zucman (PSZ) on income inequality reveals significant differences in methodology and results. PSZ report a rise in the top 1% income share from 9.1% to 15.6% between 1979 and 2015, while AS find a smaller increase from 7.2% to 8.5%. Key discrepancies arise from how underreported income, retirement income, and sales taxes are treated. AS attribute 80% of the gap to these factors, noting PSZ's allocation of corporate retained earnings and sales taxes may overstate inequality. AS's reliance on IRS audit studies and their treatment of offshore wealth suggest a more modest rise in inequality. The choice of unit analysis and ranking methodology further explains the divergence, with AS focusing on individuals ranked by size-adjusted income. These methodological differences underscore the complexity of measuring income concentration and highlight the importance of transparency in economic research.




