Thirlwall’s law, given by the ratio of the rate of growth of exports to the income elasticity of imports is a key result of Balance of Payments (BOP) constrained long run growth models with balanced trade. Some authors have extended the analysis to incorporate long run net capital flows. We provide a critical evaluation on these efforts and propose an alternative approach to deal with long run external debt sustainability, based on two key features. First, we treat the external debt to exports ratio as the relevant indicator for the analysis of external debt sustainability. Second, we include an external credit constraint in the form of a maximum acceptable level of this ratio. The main results that emerge are that sustainable long run capital flows can positively affect the long run level of output, but not the rate of growth compatible with the BOP constraint, as exports must ultimately tend to grow at the same rate as imports. Therefore, Thirlwall’s law still holds. JEL codes: F43, F32, O41

中文翻译：

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瑟尔沃尔定律、外债可持续性以及受国际收支约束的产出水平和增长率

瑟尔沃尔定律由出口增长率与进口收入弹性的比率给出，是国际收支 (BOP) 限制贸易平衡的长期增长模型的关键结果。一些作者将分析扩展到纳入长期净资本流动。我们对这些努力进行了批判性评估，并基于两个关键特征提出了应对长期外债可持续性的替代方法。首先，我们将外债与出口的比率作为分析外债可持续性的相关指标。其次，我们以该比率的最大可接受水平的形式包含外部信贷约束。出现的主要结果是可持续的长期资本流动可以对长期产出水平产生积极影响，但不是与国际收支约束相容的增长率，因为出口最终必须以与进口相同的速度增长。因此，瑟尔沃尔定律仍然成立。JEL 代码：F43、F32、O41