摘要：许多经济学教科书都认为流转税一般会造成社会福利的“无谓损失”或“超额负担”，本文认为，至少在劳动力供应没有弹性的情况下，这个看法并不准确。本文的一般均衡模型表明，如果所有产品市场均为完全竞争，那么在最优的流转税下，无论是基于“等价变动”或“补偿变动”的社会福利损失均为零。如果市场不是完全竞争，那么最优的流转税体系应使得所有产品的勒纳指数(Lerner Index)均等化。并且，最优的流转税一般可实现社会福利的潜在帕累托改进，即税收的超额负担为负。
关键词：流转税，无谓损失，超额负担，最优税收，不完全竞争
Optimal Indirect Tax and Social Welfare
Hao Wang
Abstract: Many economics textbooks suggest that indirect tax (or excise tax, consumption tax, commodity tax, etc.) usually generates “deadweight loss” or “excess burden” to the society. Using a general equilibrium model, this paper shows that this insight may be incorrect, at least when labor supply is highly inelastic. If all product markets are perfectly competitive, the optimal indirect tax structure is efficient in the sense that it invokes zero welfare loss in term of either “equivalent variation” or “compensating variation”. If not all product markets are competitive, the optimal indirect tax structure should equalize the Lerner indexes of all products, which means governments should impose light taxes on monopolistic firms or industries, but heavy taxes on competitive firms or industries. Furthermore, the optimal indirect tax under imperfect competition generally leads to potential Pareto improvement to the society.
Keywords: Indirect tax, Deadweight loss, Excess burden, Optimal tax, Imperfect competition
JEL codes：D59, H21, L16
