How the AI share of US market cap is built

Methodology version 1.0. List date Oct 2, 2026.

This index

The members' combined value divided by the value of every US-listed common stock, primary share class only, delisted companies included in the past.
Private members count on both sides of the division, so the share stays below 100%.

Every index is built from the same list of US companies building AI, chosen by our editors. A change to the list applies from its own date and never rewrites earlier days.
Share counts and earnings come from filings made by each day, so a later restatement never changes an old value.
Before the list date the values are a back-test of the companies picked that day, each from its first trading day.
A day whose prices cover too little of the index, or whose level moves more than 8%, is held for review before it is published.

Sources: company filings, exchange prices and secondary-market trades.