This article clari es the roles played by trade policy, in contrast with iceberg transport cost, in the popular setting of Melitz (2003), and characterizes the optimal reciprocal trade policy in such a setting. I show that import tariffs and iceberg transport cost are not equivalent in the strength of their trade- restricting effects and their welfare implications. With all the conflicting effectsof import tariffs on welfare considered, the optimal degree of reciprocity in multilateral tariff reduction turns out to be free trade.

中文翻译：

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降低关税的最佳互惠程度

本文阐述了在梅利兹（Melitz，2003）的流行背景下，贸易政策与冰山运输成本相比所起的作用，并刻画了在这种背景下的最优互惠贸易政策。我证明，进口关税和冰山运输成本就其贸易限制作用和对福利的影响而言，并不相等。考虑到进口关税对福利的所有冲突影响，多边关税削减中的最佳互惠程度被证明是自由贸易。