The Gravity Model
回顾了引力模型在经济学中的最新发展，包括理论基础的深化和更准确的估计方法，并提出了未来研究方向。
Gravity has long been one of the most successful empirical models in economics. Incorporating deeper theoretical foundations of gravity into recent practice has led to a richer and more accurate estimation and interpretation of the spatial relations described by gravity. Wider acceptance has followed. Recent developments are reviewed here, and suggestions are made for promising future research.