TSM Insider Trading

What Form 4 actually tells you

Officers, directors and anyone holding more than 10% of a company must report trades in its stock to the SEC within two business days, on Form 4. The filings are public the moment they land, and every row above links to the original.

Buys and sells are not symmetric

This is the thing worth internalising. An insider sells for a hundred reasons that say nothing about the company — diversification, a house, a tax bill, or a pre-scheduled 10b5-1 plan set up months earlier. An insider buying on the open market with their own money has exactly one obvious motive.

Which is why this page shows only open-market purchases and sales. Form 4 also reports option grants, option exercises and shares withheld to cover taxes; those are compensation mechanics, and screens that fold them in produce noise that looks like signal.

Why cluster buying is the part worth watching

A single insider buying tells you very little. They may be topping up after a sale, converting a bonus, or simply buying because they always buy in January. The signal researchers actually find informative is a cluster: several different insiders at the same company, buying on the open market, independently, inside a short window.

That is hard to explain away as personal circumstance. It usually means several people with the same non-public view of the business reached the same conclusion at once. The table above lists companies where three or more distinct insiders bought within 90 days — and it is worth noting how short that list usually is. Genuine clusters are rare, which is rather the point.

Timing and limits

• Reported within two business days of the trade — fast by disclosure standards, but not instant.
• Some prices are blank in the original filing, usually for gifts or transfers at no stated price. Blank here means blank there; nothing is imputed.
• This holds a rolling recent window rather than all of EDGAR history. A full backfill is hundreds of thousands of requests and would be rude to the SEC's servers.

Where this comes from

Parsed directly from SEC EDGAR — the daily filing index, then each Form 4's XML. Public domain, no vendor in between, which is why the original filing can be linked from every row.