There's been a bit of chatter in the blogosphere about a recent post on Ezra Klein's blog, featuring estimates from various economists about the revenue-maximizing tax rate. It won't come as a surprise that people on the right tended to give lower estimates and folks on the left had higher guesses. Donald Luskin of National Review estimated 19 percent, for instance, while Emmanuel Saez, Dean Baker, Bruce Bartlett, and Brad DeLong all gave answers around 70 percent.
There are two things that are worth noting.
First, every single answer is to the right of the Joint Committee on Taxation. The revenue-estimators on Capitol Hill assume that taxes have no impact on overall economic performance. As such, even confiscatory tax rates have very little impact on taxable income. The JCT operates in a totally non-transparent fashion, so it is difficult to know whether they would say the revenue-maximizing tax rate is 90 percent, 95 percent, or 100 percent, but it is remarkable that a mini-bureaucracy with so much power is so far out of the mainstream (it's even more remarkable that Republicans controlled Congress for 12 years, yet never fixed this problem, but that's a separate story).
Second, very few of the respondents made the critically important observation that it should not be the goal of tax policy to maximize revenue. After all, the revenue-maximizing point is where the damage to the overall economy is so great that taxable income falls enough to offset the impact of the higher tax rates. Greg Mankiw of Harvard and Steve Moore of the Wall Street Journal indicated they understood this point since they both explained that the long-run revenue-maximizing rate was lower than the short-run revenue-maximizing rate. But Martin Feldstein of Harvard explicitly addressed this issue and hit the nail on the head.
Why look for the rate that maximizes revenue? As the tax rate rises, the "deadweight loss" (real loss to the economy) rises. So as the rate gets close to maximizing revenue the loss to the economy exceeds the gain in revenue.... I dislike budget deficits as much as anyone else. But would I really want to give up say $1 billion of GDP in order to reduce the deficit by $100 million? No. National income is a goal in itself. That is what drives consumption and our standard of living.
For more information, I think my three-part video series on the Laffer Curve is a good summary of the key issues. I posted them in May 2009, but Cato-at-Liberty has been growing rapidly and many people have not seen them. Part I addresses the theory, and explicitly notes that policy makers should target the growth-maximizing tax rate rather than the revenue-maximizing tax rate. Part II reviews some of the evidence, including analysis of the huge increase in taxable income and tax revenue from upper-income taxpayers following the Reagan tax-rate reductions. Part III looks at the Joint Committee on Taxation's dismal performance.