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Criteria current as of: October 2026; weighting changes effective November 1, 2026 are described below. Markets enter a Belief Index series by passing a published, rules-based screen – not because someone liked them. This page specifies the eligibility criteria a prediction market must meet to enter a series, and the formula that determines how much weight it carries once admitted.
This page covers which markets enter an index and at what weight. For how admitted markets are valued, see Index Calculation Methodology. For how composition evolves over time, see Perpetual Series.
Current thresholds, published and governed. These criteria describe how Belief Systems constructs and reconstitutes its indices today. They are revised prospectively and only under the change discipline in Index Governance – announced at least five calendar days before effect, never applied retroactively. Some live series predate the current rule set, so readers may observe compositions that would not result from applying today’s criteria; that grandfathering is disclosed, not an error.

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One Rule Set, Applied Twice

There are two moments a market can enter a series:
  1. At series creation, when the initial composition is assembled.
  2. At reconstitution, when a Perpetual series adds markets on its published review cadence.
Both paths read from a single canonical rule set – the same thresholds, the same weighting formula. A market that qualifies at creation would qualify at reconstitution, and vice versa. Any divergence between the two paths is treated as a defect, not a feature. This is the same discipline that makes an equity index investable: the rules are the methodology, and the methodology does not bend per event.

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Eligibility Screens

A candidate market must pass every screen below. These are hard thresholds, applied identically to every candidate. From November 1, 2026, eligibility measures the outcome an index holds and weighting measures the market as a whole.
Thresholds are stated as current values. They are revised deliberately and prospectively – see How Thresholds Are Set below. A revision never retroactively changes an existing composition.

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Judgment Screens

Quantitative screens establish that a market is investable. A second set of screens, applied through human review, establishes that it belongs: A series targets 5 to 20 constituent markets. Below five, a single market’s resolution moves the index too violently for “diversified” to mean anything. Above roughly twenty, additions tend to either duplicate existing exposure or reach below the quality bar. A narrow theme with seven strong candidates makes a perfectly good basket; a broad theme with thirty is trimmed for clarity.

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Weighting

Admitted markets are weighted by a published formula rather than discretion:
In plain English: a market earns weight by being both deep and actively traded. The geometric mean means neither input can carry the other – a deep but dormant market, or a busy but shallow one, earns less weight than a market that is both. The square root dampens outliers so a single very large market cannot mechanically dominate the basket. From November 1, 2026: raw_score = sqrt(market_depth × 30d_average_daily_volume). Market depth is the number of contracts resting in the best five price levels on each side of the market’s order book. Each contract pays $1, so depth is in dollars of payout, and it’s the same whichever outcome an index holds. Volume is the market’s average daily trading volume over 30 days. A market with no trades at all counts as zero. If a market’s 30-day volume isn’t available, it keeps its current weight. A market listed less than 30 days is averaged over the days it’s been listed (at least 7). If a market can’t be priced, has closed, or is held at zero weight, it keeps its current weight. At a pair’s re-weighting, it gets the average of its two weights. The two Perpetual indices in a linked pair get the same weights, computed once for the pair. Until then, order-book depth is measured in dollars on the order book of the outcome each index holds. Two adjustments are applied to the natural weights:
1

Concentration cap – no market above 50%

Any market whose weight exceeds 50% is capped there, and the excess is redistributed proportionally across the uncapped markets. This repeats until no market is over the cap. The cap is anti-concentration: an index should never be one market wearing a costume.
2

Investability floor – no new market below 1%

A new market whose weight works out below 1% isn’t added. Markets already in the index are kept. This is an inclusion rule, not a weight clamp – survivors keep their relative weights. The floor is anti-fragmentation: a position too small to hold materially adds operational surface without adding meaningful exposure.
Final weights are normalized to sum to exactly 1.0. Both inputs – depth and volume – are observed at composition time, so weights are a point-in-time snapshot. They do not drift with market conditions between reconstitutions; see Known Limitations. From November 1, 2026, final weights are rounded to eight decimal places and add up to exactly 1.0. Any rounding remainder goes to the largest market that stays within the cap. The cap applies when weights are set. When a market exits at settlement or is deleted, the remaining weights scale up in proportion. That can take a market above the cap until the next review that sets weights.
Three candidate markets pass all eligibility screens:Market A’s natural weight (68.2%) exceeds the 50% cap. It is capped at 50%, and the remaining 50% is split between B and C in proportion to their raw scores:No market falls below the 1% investability floor, so no exclusions apply. In a larger basket, a market whose natural weight computed to, say, 0.4% would be dropped and the remaining weights renormalized.
Each series records its weighting scheme in its methodology, displayed on the series detail page. The formula above is the standard scheme for series created and reconstituted under the current methodology; some earlier series record a simpler scheme, such as equal weighting.

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Constituents From More Than One Venue

A standalone Perpetual index may draw constituents from more than one connected venue. For each index, we name the eligible market families on each venue and consider only the most liquid candidates. Every candidate passes the same screens and is weighted by the same formula, whatever its venue. Volume is measured the same way everywhere: contracts traded, at $1 each, excluding block trades. An event listed on two venues is held once. Linked index pairs draw from their current venue only.

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How Thresholds Are Set and Revised

The numeric thresholds are not arbitrary. They are derived empirically from the distribution of markets actually held by live Belief indices – anchored near the conservative end of that distribution, so the screens encode what has historically made a good constituent rather than a hopeful guess. Revisions follow the same discipline as the rest of the methodology:
  • Thresholds are reviewed on a deliberate cadence, not tuned ad hoc.
  • Any revision applies prospectively – to future selections, never to existing compositions.
  • The current values are published on this page, and the “current as of” date at the top reflects the last review.

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What These Rules Do Not Decide

  • Removals. Markets are removed only on published grounds, never on price or performance. Constituents exit a series by resolving – from 2026-09-30, a resolved constituent leaves at the next scheduled review as a settlement exit, and the remaining weights are scaled up in proportion (a review that also adds markets re-weights the composition); see Perpetual Series – or through deletion at a scheduled review: failing the published maintenance criteria at two consecutive evaluated monthly reviews, or no longer passing a screen that describes the market itself (directional fit, binary outcomes only, one horizon per event, resolution clarity, or the category screens). An extraordinary integrity event is handled outside the review cycle. Each deletion states its ground, and deletion is governed by the same disclosure discipline as every other composition change – see Index Governance.
  • Valuation. How an admitted market is priced into the index value is specified separately in Index Calculation Methodology.

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Further Reading

Perpetual Series

How composition evolves through reconstitution, and how costs are disclosed.

Index Calculation Methodology

How constituent prices become an index level – transparent and replicable.

Index Series

Foundational concepts: composition, normalization, lifecycle.

Risk Factors

Risks including concentration, correlation, resolution, and reconstitution.