Do assumptions about undetected tax noncompliance understate rising top income concentration?
Core argument: The authors argue that Auten and Splinter's assumption that random audits detect noncompliance equally well in the bottom 99% and the top 1% reduces measured growth in the top 1% share of pre-tax national income by 0.46 percentage points.
We argue that Auten and Splinter [AS] results are driven by the assumption that detection of noncompliance in random audit data is equally good in the bottom 99% as in the top 1%. This reduces the growth in the share of pre-tax national income held by the top 1% by 0.46 pp. We argue that the rise of pass-through business income since 1986 likely causes this bias to grow significantly over time, leading to an understatement of the increase in inequality. We also review related methods by Piketty, Saez, and Zuckman [PSZ]. These authors’ methods are rooted in the assumption that if reported income grows in concentration, then so should unreported income. We propose a simple alternative method that explicitly imposes this via a distributional neutrality assumption. Under this assumption, growth in the top income share increases by 0.52 pp.


