Gravity Models in International Trade Analysis

Gravity models form the backbone of empirical international trade analysis by positing that bilateral trade volumes are directly proportional to the economic “mass” of two countries—typically measured by GDP—and inversely proportional to the distance or other trade frictions between them. Originating from an analogy to Newton’s law of universal gravitation, these models have evolved from simple log-linear formulations to structurally consistent estimations that account for multilateral resistance, heterogeneity in trade costs and policy regimes, and zero trade flows. Modern gravity frameworks employ fixed-effects techniques to absorb unobserved partner-specific and time-varying factors, while Poisson Pseudo-Maximum Likelihood (PPML) estimation has become the standard for addressing heteroskedasticity and the prevalence of zero observations. Extensions integrate rich datasets on non-tariff barriers, digital connectivity and global value chains, and increasingly utilise machine learning for improved predictive performance. Policymakers and analysts employ these models to quantify the impact of free-trade agreements, tariff liberalisation, logistical improvements and product characteristics on trade flows, thereby informing trade negotiations and development strategies with robust counterfactuals.

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Gravity Models in International Trade Analysis publication trend

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Technical terms

Gravity equation: An empirical specification modelling bilateral trade as a function of economic size and trade costs.

Multilateral resistance: A concept capturing how a country’s overall trade barriers affect its bilateral trade relations with all partners.

Poisson Pseudo-Maximum Likelihood (PPML): An estimation technique suited for gravity models that handles zero trade flows and heteroskedasticity.

Product complexity: A measure of the technological sophistication and capability requirements of exported goods.

Relatedness: The degree to which products or industries share common inputs, technologies or knowledge bases.

References

1. Relatedness and product complexity meet gravity models of international trade. Journal of Open Innovation: Technology, Market, and Complexity (2024).
2. A re-assessment of the heterogeneous effect of trade agreements using intra-national trade flows. Economic Analysis and Policy (2023).
3. Estimating the effects of non‐discriminatory trade policies within structural gravity models. Canadian Journal of Economics/Revue canadienne d économique (2021).