Robinson's derivation of the Marshall‐Lerner condition (ML) is more general in that she considers a situation where initially the trade balance is not in equilibrium with the incorporation of the supply curves of exporters. This paper examines a partial equilibrium analysis of a country's imports and exports markets within a theoretical model which considers both the demand and supply sides in these two internationally traded‐goods markets. The aim here is to show explicitly how the Generalized Marshall‐Lerner condition (GML) of Robinson can be obtained. We examined the two effects of the nominal depreciation of the domestic currency on the trade balance: the volume effect and the value effect and how they counterbalance each other. We found that the standard Marshall‐Lerner condition (ML) was not sufficient when the trade balance was initially in deficit and it was also not necessary if the trade balance showed an initial surplus. Moreover, this study provides a new interpretation for Robinson’ sufficiency condition where the trade balance must improve following a nominal depreciation of domestic currency when the elasticity of foreign demand exceeds the ratio of imports to exports. This paper also examines the situation of a small open economy which could not influence the world prices where the foreign demand for exports and the foreign supply of exports are infinitely large. Finally, there is a discussion on two policy implications for exchange rate regulation: the amount of devaluation that is necessary to improve a given trade imbalance as a governments intervention and additional support for the slow improvement of the trade balance in the short run after a devaluation policy known as the J‐Curve effect.

中文翻译：

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一个明确的局部平衡模型来证明广义Marshall-Lerner条件（GML）

罗宾逊对马歇尔-勒纳条件（ML）的推导更为笼统，因为她考虑了一种情况，即最初的贸易平衡与纳入出口商的供给曲线之间并不平衡。本文在一个理论模型中研究了一个国家的进出口市场的局部均衡分析，该模型同时考虑了这两个国际贸易商品市场的需求和供给。这里的目的是明确显示如何获得Robinson的广义Marshall-Lerner条件（GML）。我们研究了本币名义贬值对贸易差额的两种影响：数量影响和价值影响。效果以及它们如何相互抵消。我们发现，当贸易差额最初处于赤字状态时，标准的马歇尔·勒纳条件（ML）是不够的，也没有必要如果贸易差额显示有初始盈余。此外，这项研究为鲁滨逊的充足条件提供了新的解释，即当外国需求的弹性超过进出口比率时，贸易平衡必须随着本国货币名义贬值而改善。本文还研究了一个开放的小型经济体的情况，这种情况不会影响世界价格，而外国的出口需求和出口的外国供应量是无限大的。最后，讨论了汇率调控的两个政策含义：作为政府干预，为改善给定贸易不平衡所必需的贬值金额，以及在贬值后短期内缓慢改善贸易平衡的额外支持称为J曲线效应的政策。