An elasticity of taxable income to the after-tax share of 0.2. That seems low, but what do I know? But 85 years was a long time ago: this seems only a data point telling us a little about where the envelope of possibilities lies: **Christina D. Romer and David H. Romer** (2011): *The Effect of Marginal Tax Rates: Evidence from the3 Interwar Era*: "This paper uses the interwar period in the United States as a laboratory for investigating the incentive effects of changes in marginal income tax rates. Marginal rates changed frequently and drastically in the 1920s and 1930s, and the changes varied greatly across income groups at the top of the income distribution...

...We examine the effect of these changes on taxable income using time-series/cross-section analysis of data on income and taxes by small slices of the income distribution. We find that the elasticity of taxable income to changes in the log after-tax share (one minus the marginal rate) is positive but very small (approximately 0.2) and precisely estimated (a t-statistic over 6). The estimate is highly robust. We also examine the time-series response of available indicators of investment and entrepreneurial activity to changes in marginal rates. We find little evidence of an important relationship, suggesting that the long-run productivity effects of changes in marginal rates may also be small...

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