Chokepoint transit stress nowcast

Method

For each of seven chokepoints, the endpoint averages n_total over the latest seven days and compares it with the preceding 90-day average, covering days -96 through -7 relative to the latest date.

Stress is red when deviation <= -0.15, amber when -0.15 < deviation <= -0.05, and green when deviation > -0.05. Red and amber chokepoints trigger the trade-at-risk calculation.

The trade calculation reads the latest available BACI bilateral year. Positive bilateral flows are mapped to chokepoints with a static continent-cluster sea-route heuristic, and a flow is counted for both its exporter and importer when at least one currently stressed chokepoint lies on the route.

Trade-at-risk is returned in thousands of USD. BACI values are thousands of USD and must be multiplied by 1,000 for display. Exposure share divides that value by the country's total exports plus imports.

The route returns the top 20 countries by exposed bilateral value, together with the stressed chokepoint codes contributing to each total.

The route heuristic follows continent-cluster origin-destination mapping. It models no vessel class, draft, canal fees, insurance, Arctic routes or Panama bypasses; it does not differentiate containerised, bulk and tanker cargo; intra-regional short-sea flows are marked none.

The related chokepoint workbench also reports static 30-day closure exposure as WORLD_USD times published chokepoint share times 30/365, and concentration ratios as the cumulative shares of the top N exporters.

Equations

Validation

• Direct inspection on 2026-08-27 found 18,907 daily rows for exactly seven chokepoint codes, covering 2019-01-01 through 2026-05-24.
• The endpoint reports the actual maximum source date and computes data_lag_days at request time, so stale source data is visible in the response.
• The route and page use the same routeChokepoints function and the same seven-code CHOKEPOINTS registry, preventing a separate UI routing implementation.
• The named sources provide no forecast backtest or external benchmark for the deviation thresholds or trade-at-risk heuristic.

Limitations

• This is an observed transit-deviation indicator, not a price forecast, welfare model or general-equilibrium estimate.
• The shipped PortWatch parquet ends on 2026-05-24. On the 2026-08-27 verification date that is a 95-day lag, contradicting the page's near-real-time 4-7 day description and 2019-present label. The endpoint itself exposes the lag honestly.
• Only ISO3 codes present in the static REGION_OF mapping enter the trade-at-risk calculation. Flows involving an unmapped country are skipped.
• The continent-cluster heuristic does not model actual vessel tracks, vessel class, draft, canal fees, insurance, weather, alternative straits, Arctic routing or cargo type.
• Intra-regional and direct trans-Pacific or trans-Atlantic flows can receive zero exposure even when an actual sailing transits a strait of opportunity.
• When the 90-day baseline is zero, the implementation sets deviation to zero and therefore labels the chokepoint green.
• The trade-at-risk total is static exposure accounting. It does not model rerouting, inventory buffers, substitution or welfare loss.
• The country denominator map does not aggregate duplicate ISO3 reporter rows before assignment, so historical duplicate reporters can affect exposure shares.
• If portwatch_chokepoints is absent or empty, the route returns HTTP 503.

References

• IMF PortWatch Daily Chokepoints.
• Halim et al. (2018), Decarbonization Pathways for International Maritime Transport, Transportation Research Part D 64: 12-32.
• Notteboom, Pallis and Rodrigue (2022), Port Economics, Management and Policy, chapter 5.
• UNCTAD, Review of Maritime Transport 2024, chapter 3.
• US Energy Information Administration, World Oil Transit Chokepoints.
• Panama Canal Authority, Annual Report 2023.
• Guinea and Baumeister (2024), Global supply chains and the volatility of oil prices, Journal of International Money and Finance 148, 103172.
• OECD (2023), Maritime supply chains and chokepoint exposure.

Endpoints