SIF-50 v1

SIF-50 methodology

The SIF-50 is a paper index benchmark built from real, signed market data. This page documents exactly how the 50 constituents are chosen, how they are weighted, when the basket changes, and where the methodology falls short. No step here is hidden or editorial: it is data plus a fixed procedure, laid out below.

What the index level means

The SIF-50 index level is the weighted average of its constituent prices, in US dollars. It is not normalized to a 100 base. When you see a level like $3.89, that is a literal dollar-weighted average price, not a rebased index point. The headline series to track is the cumulative return since genesis (the percent change from the SIF-50 v1 genesis NAV), not the raw dollar level by itself.

Selection criteria

Universe

The candidate universe is the top ~200 most popular items on the Steam Community Market search, pulled by the popularity sort.

Eligibility

An item survives the pre-filter only if it is quoted by at least 2 keyless venues and its median cross-venue price falls between $2 and $2,000. Items outside that band, or with too little venue coverage, are dropped before ranking.

Ranking

Eligible items are ranked by raw 24-hour Steam Market sales volume, highest first. Ties break on venue count, then alphabetically on the market hash name. The top 50 by this ranking become the SIF-50 constituents.

Weighting

Weights are volume-proportional: an item's raw 24-hour Steam Market volume relative to the basket's total volume sets its starting weight. No single constituent may exceed a 5% weight cap. Items whose proportional weight would exceed the cap are fixed at 5%, and the remaining budget is redistributed proportionally over the uncapped items, repeated (water-filling) until every weight is at or under 5% and the 50 weights sum to 1.

Rebalance policy

Frozen basket

The SIF-50 composition and weights are frozen per version. There is no continuous rebalance: the basket does not silently drift week to week.

Version bump on change

Any change to composition or weights, for any reason, bumps the version (SIF-50 v1 to SIF-50 v2, and so on) and is recorded below in version history. A silently edited basket would destroy the credibility of the index, so this repo does not allow it.

Coverage policy

Each NAV point is computed from same-day median quotes across keyless venues. Constituents that have no valid quote that day are dropped and the remaining weights are renormalized over the covered subset, so one missing quote never zeroes the index. Publishing a new weekly data point additionally requires at least 40 of the 50 constituents to have a valid quote that day. On thinner coverage, no data point is published for that week rather than publishing a distorted or partial NAV.

Composition, honestly

Ranking by raw 24-hour Steam Market volume makes the SIF-50 case-heavy: 17 of the 50 constituents are weapon cases (21 of 50 if souvenir and collection packages are also counted). Weapon cases are consistently CS2's most-traded items on Steam Market, so a volume-ranked, liquidity-weighted index concentrates in them by construction. That is a property of this methodology, not an editorial choice to favor cases over skins.

Version history

Version Date Note
SIF-50 v1 2026-07-08 Frozen genesis basket. Genesis NAV $3.89.

Download the data

CSV download: the full NAV history is published at fund-data/sif50.csv. Schema: date (ISO 8601), navUsd (index level in US dollars), cumulativeReturnPct (cumulative return since genesis, percent), covered (constituents with a valid quote that day, out of 50), version (the SIF-50 version that produced the row).

Limitations

  • Pricing and eligibility use keyless-venue coverage only; venues that require an API key or manual auth are not part of this ranking pass.
  • Cross-venue prices are aggregated by median, not a full order book, so the NAV does not reflect the price of any single actual trade.
  • No fees, seller cuts, or slippage are modeled anywhere in this index; it is a gross, before-cost benchmark.
  • The NAV updates on a weekly cadence, not continuously.
  • 24-hour sales volume is self-reported by Valve's public Steam Market priceoverview endpoint and is not independently audited.
  • This is a paper benchmark, not investment advice, and not a tradable product. Nothing on this page is a promise about future returns.
See it live: the current curve, constituents, and named strategy baskets built on this benchmark live on the Skin Index Fund page. Every rebalance decision is recorded on the signed, hash-chained ledger you can check yourself at verify.html.