中文摘要
我们提出了一种识别帕累托改进型税制改革的新方法。该方法给出了帕累托改进型改革方向存在的充分必要条件。一个主要见解是：“两个税档就足够”：如果改变一个或两个收入税档的税率无法改进税制，那么就不存在帕累托改进型的连续改革方向。我们还说明了如何检验某项给定的税制改革是否构成帕累托改进。我们运用这些工具研究了美国于1975年引入劳动所得税抵免（EITC）的改革。一个稳健的发现是，在引入EITC之前，美国的税收—转移支付体系并非帕累托有效。在对行为反应作出合理假设的情况下，1975年的改革并不构成帕累托改进。不过，从定性角度看，该改革具备正确的特征：如果类似改革将收入补贴覆盖至更广泛的收入群体，本可以构成帕累托改进。
Abstract
We develop a new approach for the identification of Pareto‐improving tax reforms. This approach yields necessary and sufficient conditions for the existence of Pareto‐improving reform directions. A main insight is that “Two brackets are enough”: When the system cannot be improved by altering tax rates in one or two income brackets, then there is no continuous reform direction that is Pareto‐improving. We also show how to check whether a given tax reform is Pareto‐improving. We use these tools to study the introduction of the Earned Income Tax Credit (EITC) in the United States in 1975. A robust finding is that, prior to the EITC, the U.S. tax‐transfer system was not Pareto‐efficient. Under plausible assumptions about behavioral responses, the 1975 reform was not Pareto‐improving. Qualitatively, though, it had the right properties: A similar reform with earnings subsidies made available to a broader range of incomes would have been Pareto‐improving.