The Gravity Equation: To Pool or Not to Pool-A Critical Assessment
Kamel Ghaddab
What the paper says
I. IntroductionThe gravity model has become a central empirical tool in international trade, with robust predictive power and increasing theoretical refinement.While its empirical use dates back to Tinbergen (1962), the gravity equation has undergone a profound transformation over the past two decades.The foundational work of Anderson & Van Wincoop (2003) introduced multilateral resistance terms, providing a micro-founded structure that links bilateral trade flows to relative trade costs in a general equilibrium framework.This structural interpretation is complemented by Eaton & Kortum's (2002) Ricardian model, which derives trade patterns from stochastic productivity differences, and embeds the gravity equation within a richer general equilibrium framework.Parallel to these theoretical developments, empirical advances have addressed important econometric limitations.Notably, Silva & Tenreyro (2006) demonstrated that the commonly used log-linear OLS specification of the gravity equation is inconsistent in the presence of heteroskedasticity and zero trade flows.They proposed the Poisson Pseudo-Maximum Likelihood (PPML) estimator as a robust alternative, which has since become the gold standard in empirical
Evidence weight
Balanced mode · F 0.40 / M 0.15 / V 0.05 / R 0.40
| F · citation impact | 0.50 × 0.4 = 0.20 |
| M · momentum | 0.50 × 0.15 = 0.07 |
| V · venue signal | 0.50 × 0.05 = 0.03 |
| R · text relevance † | 0.50 × 0.4 = 0.20 |
† Text relevance is estimated at 0.50 on the detail page — for your query’s actual relevance score, open this paper from a search result.