How much revenue would raising top tax rates actually generate?
Core argument: A Laffer curve estimated with a tax calculator and the true tax base peaks at a top rate of 47%, yielding only 1.3% more federal individual income tax revenue, about 0.1% of GDP.
Laffer curves estimated with more realistic taxes are flatter, suggesting less potential revenue gains from top rate increases and a lower revenue-maximizing top rate. Standard simplifications miss meaningful behavioral margins such as shifting across tax bases and sectors. Interactions between federal individual income taxes and other taxes produce even flatter Laffer curves and smaller revenue gains from higher top rates. Panel A of Figure 2 shows how federal individual income tax revenues change as the top tax rate varies along the x-axis. With a broad base, total income enters the tax function as a single base, applying the top rate to all income even though much of it qualifies for lower preferential tax rates. With a narrow base, only wage income enters the tax function, which fails to apply the top tax rate to any capital income. The true tax base lies between the narrow and the broad base. The Laffer curve estimated using the tax calculator and true base reaches a more modest peak (only 1.3% more tax revenue) at a top tax rate of 47%. Notably, this additional federal income tax revenue is only about 0.1% of GDP. Relative to both the narrow and broad bases, the true base implies smaller potential revenue gains and a lower revenue-maximizing top tax rate.


