This paper updates a review conducted by the Congressional Budget Office (CBO) in 1996 in which the agency evaluated the academic research on the effects of changes in after-tax wages on labor supply in the U.S. economy. That review concluded that substitution elasticities were larger in absolute value than income elasticities and that the decision to work was more responsive to after-tax wages than was the choice of hours. In this update, we find that for men and single women, estimates of substitution elasticities have increased, and income elasticities still appear to be smaller in absolute value than substitution elasticities. We also find that labor supply elasticities of married women have fallen substantially in the last three decades, although they are still higher than the elasticities of men and unmarried women. Based on our review, the elasticities of broad measures of income (total income less capital gains) from tax return data are in most instances consistent with the labor supply elasticities estimated using survey data. We find little compelling evidence that high-income taxpayers have substantially higher elasticities with respect to their labor input than other taxpayers: While some studies have estimated higher elasticities of broad income among high-income taxpayers, those results appear to reflect those taxpayers’ greater ability to time their income. In contrast, we find evidence that low-income workers have higher elasticities of labor supply than other workers, especially in the component of their labor response that reflects movement in and out of the workforce.