Trimtabist

Berth hours track imports — not total trade — and one gateway tracks nothing

mechanism · 2018-01 → 2024-12 (672 zone-months) · verdict: MECHANISM + ONE EXCLUSION

What was registered, before the data was touched

Cross-check CHK-003: if AIS berth activity measures trade, it should correlate with census tonnage within each gateway across 7 years. Tested against imports and against imports+exports.

What the record shows

Across 174,440 vessel stays, berth hours correlate with import tonnage at r = 0.56 pooled within-zone (n = 672) — NY-NJ r = 0.77, Houston 0.70, LA/LB 0.64. Adding exports makes the fit worse at all eight gateways: discharge time drives the berth stay; export loading does not add proportional time. And one gateway fails outright: Seattle–Tacoma reads r = 0.01 — its berth activity doubled 2021–2024 against flat trade, which is operational tempo (the ILWU slowdown era, berth shifting) plus Alaska domestic services invisible to trade data. It is excluded from every volume claim this site makes. Two further contaminations are on the record: Charleston and Norfolk carry 76% and 42% of berth-time under US flags — largely Ready Reserve Force hulls parked for months — which inflates levels but survives demeaning.

Berth hours vs census import tonnage, monthly within each gateway, 2018–2024 (84 months each).

What would prove this wrong

A gateway where the imports+exports fit beats the imports-only fit would break the discharge-time mechanism; none of the eight does.

Cite this

This study is a frozen artifact: the ruling and its exhibits do not change when new data lands. If the verdict is ever revised, the revision is printed here with its reason, and the original stays on the record.

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