One of the pillars of the 1957 Treaty of Rome that ultimately led to the European Union is the commitment to the four freedoms of movement (goods, services, persons, and capital). Over the following decades, as the members expanded in numbers, they also sought to deepen the integration amongst themselves in all four dimensions. This paper estimates the success of these policies based primarily on a gravity framework. Distinct from past evaluations, we augment the traditional equation for international flows with the corresponding intra-national flows, permitting us to distinguish welfare-improving reductions in frictions from Fortress-Europe effects. We complement the gravity approach by measuring the extent of price convergence. We compare both quantity and price assessments of free movement with corresponding estimates for the 50 American states.

中文翻译：

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欧洲合众国：四项自由的重力模型评估

最终导致欧盟成立的 1957 年罗马条约的支柱之一是对四项行动自由（货物、服务、人员和资本）的承诺。在接下来的几十年里，随着成员数量的增加，他们也寻求在四个维度上加深彼此之间的融合。本文主要基于重力框架估计这些政策的成功。与过去的评估不同，我们将传统的国际流量方程与相应的国内流量进行了扩充，使我们能够区分促进福利的摩擦减少与堡垒-欧洲效应。我们通过测量价格趋同的程度来补充重力法。我们将自由流动的数量和价格评估与美国 50 个州的相应估计值进行比较。