An International Trade Flow Model with Substitution: An Extension of the Gravity Model
针对传统引力模型无法描述贸易流间替代关系且缺乏理论基础的问题，提出了扩展引力模型（EGM），实证检验表明EGM优于引力模型，且引力模型高估了贸易决定因素的影响。
SUMMARY The traditional gravity model has often been applied to international trade flows, especially to analyze trade creation and trade diversion. However, there are two fundamental objections to the model: it cannot describe substitutions between flows, and it lacks a cogent theoretical foundation. A newly developed model, the Extended Gravity Model (EGM), overcomes these objections. An empirical test strongly rejects the gravity model in favour of the EGM. The empirical analysis also proves that the gravity model widely overestimates the influence of the determinants of international trade. The EGM encompasses several models originating in regional economics, and can be applied usefully to a variety of subjects.