The vulnerability of our shipping routes remains underdiscussed, perhaps that is in some ways a good thing:

We study the macroeconomic and trade-policy implications of disruptions to U.S.-bound shipping routes. Standard models treat them as iceberg-cost shocks, conflating the shock with the response to it. Using satellite vessel-tracking data, we construct route-level measures of potential and effective capacity for all U.S.-bound container ships from 2016 to 2025. Utilization losses in recent disruptions ran 20 to 40 percentage points, and began months before port congestion became visible. We embed these measures in a general equilibrium model in which firms reallocate a common fleet without internalizing the congestion they create and price above marginal cost, while importers’ sourcing responds to route profitability. The reallocation triggered by a disruption then has first-order welfare effects, and the route’s Domar weight is not a sufficient statistic for its welfare cost. The 2021 West Coast crisis and the 2023-2024 Red Sea attacks cost 0.69% and 0.35% of output. Naval protection of Red Sea shipping generated benefits of 0.04-0.08% of output at a fiscal cost of 0.02%. Tariffs decongest the routes they tax, offsetting or even reversing their conventional welfare cost.

That is from a new paper by