最適差別關稅──考慮外國廠商友善國內消費者的情況

Optimum Discriminatory Tariffs in an International Duopoly with Consumer-friendly Foreign Exporters

本文設立一個三國兩廠商的模型探討外國出口廠商對進口國消費者具友善態度時最適差別關稅政策的訂定。本文所獲的結果顯示：當廠商成本函數屬邊際成本為固定常數時，傳統低成本高關稅的課稅原則不必然會成立，最適差別關稅稅率也未必等於成本差距的一半，須視兩出口廠商對本國消費者的友善態度而定。當對本國消費者相對友善的出口廠商屬成本相對高（低）者時，低成本高關稅的課稅原則仍然（可能無法）成立，最適差別關稅稅率將高（低）於成本差距的一半。當生產技術相同時，本國政府應給予對本國消費者相對較友善的國家課徵較低的關稅稅率。

In this paper, we develop a three-country, two-company model to investigate the optimal differential tariff policy when foreign exporters are friendly to consumers in importing countries. According to the results obtained in this paper, the traditional low-cost, high-tariff principle does not necessarily hold when the marginal cost is constant, and the optimal differential tariff rate may not be equal to half of the cost differential, depending on the friendliness of the two exporters to their domestic consumers. When the exporter who is relatively friendly to domestic consumers is the relatively high (low) cost exporter, the low cost, high tariff principle still (may not) hold and the optimal differential tariff rate will be higher (lower) than half of the cost differential. When the production technologies are the same, the government should give a lower tariff rate to the country that is relatively more friendly to its consumers.