How this is built
Methodology
What data The Dwell pulls, where it comes from, and how often it refreshes.
What we pull, and from where
Three different measurements get called dwell in the port trade, and each comes from a different source, so the list runs by metric:
- Ships awaiting berth, the count of container ships waiting offshore for a berth, comes from MARAD and the Marine Exchange by way of the Bureau of Transportation Statistics port and supply-chain freight indicators. It is a weekly snapshot and the freshest signal on the site.
- Container dwell at Los Angeles, how long import boxes sit on the terminal after discharge, comes from the Port of Los Angeles Cargo Operations Dashboard, which posts a report each business day of import-container inventory in 0-4, 5-8 and 9-plus day buckets. It is the one structured daily feed of its kind; most ports publish container dwell only as monthly narrative and PDFs.
- Vessel dwell at berth, how long a ship sits at the berth from arrival to departure, is the Bureau of Transportation Statistics' archived AIS-derived dataset, carried as a labeled historical series.
From the same BTS freight-indicators table we also pull the truck planning-time index, the monthly TEU volumes (loaded imports, loaded exports and empties, per port) and railcar terminal dwell. The monthly components land about two months after the month they cover, and every figure on the site is dated to the period it reports, never to the day it was pulled. One more source rides alongside: the Port of Los Angeles's monthly import commodity mix from the US Census Bureau's international-trade data (what the port imports, by commodity chapter, in customs value and containerized weight), shown on the Los Angeles container page.
How often
The Port of Los Angeles report is ingested daily, each business day. The BTS indicators are pulled weekly, ahead of the Tuesday brief, with a trailing window so a missed run backfills on the next one. Every data page carries two dates: "data through" is the newest reading in the data itself, and "page updated" is when the page was last rebuilt.
For how to read the numbers once they are in front of you, see how to read this.
Republishing our charts and statistics
The charts and statistics on The Dwell are free to republish. Use them in an article, a report, a class, a presentation, or a post — you do not need to ask us first. We ask one thing in return: credit The Dwell with a visible link back to the page you took the figure or chart from, and keep that link live.
Every chart has an Embed chart button with a snippet you can paste straight into a web page. Because it points at the live image, the chart you embed today keeps updating itself as new data lands — you never have to swap in a fresh screenshot. Every data page, guide, and issue has a Cite button that hands you a ready-made citation line, including the date the data runs through. If you are quoting a number, keep that date: it is what tells your reader how current the figure is.