How the indices work
All indices are price-return indices. Dividends are not reinvested. Every stock index starts at 1000 on the close of 2022-11-30, the day ChatGPT launched.
Indices
| Index | Members | Weighting |
|---|---|---|
| AIX, AI Stack Index | All constituents | Each active layer counts equally. Inside a layer, weights follow capped market cap. |
| AIX-CAP | All constituents | Capped market cap across the whole universe |
| AIX-<layer> | Constituents of one layer | Capped market cap |
| PMI, Private Mark Index | Private companies with closed funding marks | Sum of latest closed marks, chain-linked |
AIX weights layers equally so that it measures the whole ecosystem. In a cap-weighted index, a handful of mega-caps would decide almost every move. AIX-CAP shows "the AI trade as investors hold it".
Weights
A company's market cap is its price times its shares outstanding. Shares come from current company profiles and are applied to the whole history. Buybacks and new issuance since 2022 make early weights slightly wrong.
Each group of n members has a weight cap of max(25%, 1.5 / n) inside a layer and max(10%, 1.5 / n) for AIX-CAP. Weights above the cap are cut to it, and the excess goes to the other members in proportion to their weights. Weights are set at each close and stay fixed through the next session.
Daily and intraday values
R(layer, t) = sum of w(i, t-1) * ( P(i, t) / P(i, t-1) - 1 )
I(layer, t) = I(layer, t-1) * ( 1 + R(layer, t) )
R(AIX, t) = average of R(layer, t) over the active layersA layer is active when it has at least 2 eligible members. A layer that becomes active starts at 1000 on that close.
During the session, the site updates once an hour with consolidated prices that are at least 15 minutes old. Each update applies the same formula with the latest delayed price in place of the close. A stock that has not traded yet today counts as unchanged.
Official closes from the consolidated tape replace the intraday values after the close. Prices are split-adjusted, so a stock split never shows up as a price move.
Membership
- A new listing joins after 5 full trading days, at its 6th close. This keeps first-day IPO swings out of the index.
- A company that delists or is acquired leaves at its last close.
- Each company has exactly one primary layer, which decides its index membership. Its other roles are shown as tags only, so no company is counted twice.
- Membership changes never cause a jump in an index, because each day's return uses the previous close's members and weights.
Private companies
A private company has valuation marks. Only closed primary rounds, tenders, and mergers count toward PMI. Reported talks and secondary-market estimates appear on charts as hollow markers.
Charts draw private valuations as a step line. The line is flat between marks, because a value between two rounds was never a real price.
PMI starts at 1000 on the first qualifying mark. A new mark moves PMI by the change in the sum of all latest marks. A company's first mark, its merger, or its listing changes PMI's membership without moving its level.
Stance verdict
Four signals each score from −2 to +2 at every close:
| Signal | +2 | +1 | 0 | −1 | −2 |
|---|---|---|---|---|---|
| Trend: AIX against its 50- and 200-day averages | above both, 50 above 200 | above the 200-day only | mixed | below the 200-day, above the 50-day | below both, 50 below 200 |
| Relative strength: AIX minus QQQ over 63 trading days | more than +5 pts | +1 to +5 | −1 to +1 | −5 to −1 | below −5 |
| Breadth: share of constituents above their 50-day average | above 70% | 55–70% | 45–55% | 30–45% | below 30% |
| Drawdown from the all-time high | within 5% | 5–10% | 10–15% | 15–25% | more than 25% |
The total maps to a label:
| Total | Label |
|---|---|
| 5 to 8 | Strong |
| 2 to 4 | Positive |
| −1 to 1 | Mixed |
| −4 to −2 | Weak |
| −8 to −5 | Stressed |
The verdict describes price action only. It is not investment advice.
Known limitations
- Current share counts are applied to history.
- Stocks listed outside the US (SK Hynix, Samsung, Tokyo Electron) are not included yet.
- Total tracked value adds public market caps and private marks. It is gross: cross-holdings, such as public companies' stakes in private labs, are counted twice.