GUIDE

Data sources and update schedule

Two public sources

The league combines two inputs. The first is SEC EDGAR, the US Securities and Exchange Commission's public filing system. From it we read the list of exchange-listed issuers, the share counts that companies report on the cover pages of their filings, and some basic registration details such as the state or country of incorporation and an industry code. The second is daily price bars from the IEX exchange, retrieved through the market-data service run by Alpaca. We use only the historical daily bars endpoint, which is a read-only data service. No trading, orders or accounts are involved.

Only the derived results are published: market cap, rank, rank change and change percentage. Raw prices and provider responses are not stored in the site's data, and the snapshot format rejects fields that would reveal them.

When snapshots are captured

A scheduled job runs once a day at 22:00 UTC. That is 6:00 pm in New York during daylight saving time and 5:00 pm during standard time, so it always falls after the regular US trading session has finished. The job can also be started by hand. Each run first works out which trading session it should describe, then downloads the data, derives the market caps, runs its quality checks and only then writes a new snapshot file. If any required source fails, the run stops with an error instead of publishing a partial table, and the previous snapshot stays in place.

Which session a snapshot reflects

The date on a snapshot is the completed US trading session in New York time, not the date the job ran in UTC. The rule is simple: after 4:15 pm New York time, today's session counts as complete; before that, the previous day is used. The job then looks at the most recent daily bars returned for each ticker and takes the session date shared by most of them. If the newest available session is more than a week old, the run refuses to publish.

Weekends and holidays

The schedule is daily, but the market is not. On a Saturday, a Sunday or a market holiday, the latest completed session is still the last day the market was open. When the job finds that a snapshot for that session already exists, it keeps the original and does not create a duplicate. That is why retained dates skip weekends and holidays, and why a comparison made on a Monday is usually with the previous Friday.

What is retained on this build

This version of the site retains 3 snapshots, from 2026-10-16 to 2026-10-30. The latest, dated 2026-10-30, is a Friday session; the one before it is dated 2026-10-19, a Monday. Weekdays missing between retained dates, which means a market holiday or a skipped capture: 2026-10-19 to 2026-10-30 (8 weekdays with no snapshot). Retained history is immutable: a published snapshot is never rewritten, and a missing day is never filled in after the fact.

Gaps and failures

Scheduled jobs can be delayed or skipped, and data providers can have outages. When that happens there is simply no snapshot for that session. We do not interpolate, copy forward or back-fill. Change percentages and rank changes always compare against the most recent snapshot that was actually retained, which can be more than one trading day earlier. The movers page states both dates so the span is always visible.

What "New" means

In the Rank change column, New means that a company appears in the selected snapshot but did not appear in the top hundred of the earlier snapshot being compared. It may have climbed in from below, or the earlier capture may have excluded it for a data reason. It does not mean the company has only just been listed. If there is no earlier snapshot at all, no movement can be shown and the column displays a dash.

Delay and accuracy

The standings describe a closed session, so they are always at least several hours old and often more. They use the IEX close, which comes from a single exchange rather than the consolidated tape, and share counts that may be weeks out of date. The details, and how these limits affect individual companies, are covered in how the league is calculated. For a plain explanation of the number itself, see what is market capitalization.

Informational only, not investment advice.