Geopolitical conflicts and the restructuring of maritime transport networks: the causal effect of the Red Sea crisis on port throughput

The Red Sea crisis has severely impacted global shipping networks, yet its causal effects on port operations remain inadequately quantified. This study examines 16 major container ports along the Red Sea-Mediterranean route, employing the difference-in-differences method to empirically assess the net impact of the crisis on port container throughput. The analysis covers the period from Q1-2021 to Q4-2025, encompassing 672 port-quarter observations. The baseline DID regression reveals a core interaction coefficient of -0.295 after controlling for port fixed effects, time fixed effects, and a series of covariates, indicating an average 29.5% decline in throughput at treatment group ports — a result that is both statistically significant (p < 0.01) and economically meaningful. Dynamic effect analysis confirms the parallel trends hypothesis, with the negative impact intensifying post-crisis. PSM-DID tests, placebo tests, and tail-trimming procedures all validate the robustness of the findings. Heterogeneity analysis shows that hub ports experienced only approximately 43% of the impact compared to non-hub ports, while ports in low-political-risk regions demonstrated stronger resilience. This study employs rigorous causal inference methods to quantify the dynamic cumulative effects of the Red Sea crisis on port operations, providing empirical evidence and decision-making references for port resilience to geopolitical risks.