Trimtabist

The US Trade Ledger — every US container gateway, every partner country, every month. Census-recorded, AIS-verified.

← all methods · TT-002 instrument page · raw markdown: ?raw=1

TT-002 · Corridors — method

Grade: REPORTED for port calls, MODELLED for trade volumes. These are different kinds of

number and are labelled separately for that reason.

Source

IMF PortWatch (portwatch.imf.org), built by the IMF with the UN Global Platform on Kpler's AIS.

Licence permits commercial use with attribution:

"Sources: Kpler; UN Global Platform; IMF PortWatch (portwatch.imf.org)."

What each number is

Port calls — REPORTED. Counted events, but the count depends entirely on how port polygons are

drawn and how vessels are classified. Counted by an algorithm, not by a person at the quayside.

Trade volumes (import_container, export_container) — MODELLED. Estimated from vessel type,

capacity and draft. The IMF is explicit about this. Useful for direction and shape; never

quotable as a measured quantity. Any publication resting on these must say "modelled, not measured."

Coverage

20 ports · 55,100 port-days · 2019-01-01 onward. Ten US gateways, nine Indian ports, Colombo.

Refreshes weekly (Tuesday, ~09:00 ET); data lags roughly nine days.

What it cannot do

It has no origin–destination pairs. PortWatch reports each port's total activity, not who

traded with whom. "India up, Colombo down" is therefore an inference about a corridor, never a

measurement of one. Every claim built this way must be written as an inference.

Revisions

PortWatch reprocesses history. The series can change under you, so any published figure must be

pinned to the date it was retrieved. Our collector upserts on (portid, date) and silently adopts

revisions.

Known failure — the Indian series is withdrawn from 2025-03

Between mid-2025 and March 2026 this source shows Indian container port calls collapsing by up to

49%, then recovering. That collapse did not happen in the physical trade. US customs

declarations (TT-005) show imports from India flat to strongly up across exactly that window, and

goods cannot reach the United States without leaving India.

Supporting evidence that it is an upstream artifact rather than a trade event: the damage is wildly

uneven across ports (Nhava Sheva −59%, Chennai −5%, Kattupalli +52%), consistent with calls

being reassigned between port boundaries; and it affects every vessel type, including tankers

(−30%), which no container-trade story explains.

Recorded as F-001. The affected series are unreachable through every outward surface.

The honest reading: this source is dependable for long-horizon shape at aggregate level, and should

not carry a port-level claim for a specific window without a second instrument agreeing.