Introducing the STI: a market index for the CS2 skin market

When you want to know how the US stock market is doing, you look at the S&P 500. When you want to know how the Brazilian stock market is doing, you look at the Ibovespa. These indices have decades of history, public methodology, professional rebalance committees, and serve as the baseline against which any other investment is measured.

For the CS2 skin market, no such benchmark existed. You open the Steam Community Market and see ~31,000 individual prices. Each specialty site (csgoskins.gg, pricempire, csfloat) shows its own fragmented view. Nobody could answer: "how much did the entire skin market move this year?"

That's the gap STI — Skin Trackers Index fills.

What the STI is

A family of seven indices measuring CS2 skin market behavior over time, applying the same construction logic the S&P 500 uses, adapted for an alternative-asset universe.

The five "skin" indices (overlapping universes)

• STI 30 — the blue-chip basket. Top 30 skins by market cap, minimum 36 months of history, below-median volatility. Quarterly rebalance. The CS2 equivalent of the Dow Jones Industrial.
• STI 100 — mid-cap leaders. Top 100 by market cap with relaxed liquidity filters (≥30 listings, ≥24 months history). Monthly rebalance. Filters out the high-liquidity commodities and keeps skins that better represent the upper end of the market.
• STI 500 — broad market reference. Top 500 by market cap with broad filters (≥$5 price, ≥50 listings, ≥12 months). The S&P 500 of the skin market.
• STI 1000 — the long tail. Same filters as STI 500 expanded to 1,000 constituents. Captures the long tail (mid + small caps) that STI 500 leaves out.

The three "non-skin" indices (disjoint universes)

• STI Cases — containers. Top 40 cases by market cap. Drop removal by Valve creates structural scarcity without float risk. Compounded at +788% over 6 years (vs the broad market's +65%) for reasons covered in the supply-scarcity post.
• STI Stickers — tournament foils + capsules. A more recent index covering the cosmetic-sticker market (Major sticker capsules + foil patches).
• STI Agents — character skins. The smallest universe, but with its own scarcity dynamics (operation-specific issuance, specialist rare agents).

How the indices work, in three steps

The mechanics are identical to traditional financial indices. At each rebalance date (monthly for STI 100/500/1000/Cases, quarterly for STI 30 — see the rebalance cadence post for the trade-off), the algorithm:

1. Selects skins that meet the objective criteria — minimum price, minimum active listings, minimum time on market.
2. Computes weights proportional to each skin's market cap (more valuable skins weight more, the same logic the S&P 500 uses).
3. Adjusts the divisor so the index value doesn't jump artificially when a skin enters or exits the basket — covered in detail in the divisor-adjustment post.

The result is a monthly time series, base 100 at April 2020, that you can compare against any other asset.

Why this matters

For the investor / trader

If you allocate to skins, the STI 30 tells you whether your individual portfolio is beating the market or not. Up 20% in 2 years? STI 30 was up 10% in the same window? You generated alpha. Down 5% while STI 30 was up 15%? You lost relative performance. Without the index, you only had CDI or Bitcoin as benchmarks — neither of which represents "the skin market itself."

For the analyst / researcher

All data is exposed via public API. Download the monthly snapshots, regress against CS2 player count (the correlation has nuance: r=0.82 in levels, r=0.26 in returns, ~0 trailing 12mo — each interpretation different), compare against Bitcoin volatility, or just plot the chart yourself. No black box.

For the curious

The STI is a simple way to look at the skin market as a whole. The home-page chart shows 6 years on one screen: the pandemic-era rally (2020-2021), the pre-CS2 peak (late 2023), the 30% drawdown in 2021, the gradual recovery from 2024 onward. It's a direct visual reading of what happened.

Quick macro context

One thing that becomes obvious looking at the chart: the skin market doesn't move in a vacuum. It responds to the same global liquidity tide that moves equities, crypto, and real estate.

Between 2020 and 2021, during the pandemic, the Fed cut US rates to zero and expanded the monetary base by trillions via QE. Brazil's central bank dropped Selic to a historic low of 2% in August 2020. Cheap money inflated risk assets globally — equities hit highs, Bitcoin went from $6K to $69K, and CS2 skins had their first historic peak.

From 2022, the cycle reversed. Fed hiked aggressively to fight inflation; Brazilian Selic jumped from 2% to 13.75% by 2023. Risk assets lost fuel. Not a coincidence that STI 30's deepest drawdown was April-December 2021 (-30.8%) — exactly when the market started pricing the monetary tightening cycle.

That's why comparing skins to CDI over the last 6 years isn't apples-to-apples: CDI compounded at ~10%/year (~+77% cumulative) because Selic was historically high in 2022-2024, not because fixed income is "always better." The full cross-asset breakdown is in the STI vs S&P 500 vs Bitcoin post.

Transparency and methodology

The rule: everything a serious analyst would need to challenge the numbers is documented. The methodology page covers inclusion criteria, divisor formula, weighting scheme, rebalance cadence, and raw-data availability via the public /api/indices endpoint. Implementation details available on request via /en/sobre.

Updates are automatic:

• Daily cron at 00:00 BRT collects fresh Steam Market price snapshots.
• On the 3rd day of each month, the full history is refreshed and indices are recomputed.
• Each month adds another data point to the series — the curves keep growing without manual intervention.

If the project shuts down, the data lives in the public GitHub repo. If a methodology rule changes, the audit trail is documented in docs/audits/.

Honest disclosure on what the STI can't do

Same caveats as everywhere else:

• Past performance is not a forecast. The 6-year backtest is one specific window; the next 6 years could look very different.
• Period sensitivity matters. 2020-2026 included the post-COVID rally + AI bubble; equities returns in this window are above their long-term average. A different window would tell a different story.
• Friction matters. Gross returns don't account for the 15% Steam fee + spread + tax — covered in the liquidity-penalty post. Realised net returns can be 30%+ below the gross headline.
• Float and pattern aren't in the index. Skin × wear × StatTrak are separate assets, but float-within-wear isn't — known limitation, on the methodology page.

Where to start

For a panoramic view of the broad market, STI 500 is the natural starting point:

→ STI 500 — the broad market index

For mid-cap movement:

→ STI 100 — the mid-cap layer

For the tightest, most stable basket:

→ STI 30 — the blue-chip basket

For the supply-restricted segment that compounded at +788%:

→ STI Cases — the containers index

Bottom line

The CS2 skin market is large enough and liquid enough to deserve a real benchmark. The STI family is what one looks like when you apply S&P-style methodology — public rules, divisor-adjusted continuity, monthly snapshots, no commission, no marketplace conflict.

The mechanics are S&P 500. The asset class is CS2 skins. The result is a benchmark anyone can use, replicate, or challenge.

Fernandes, J. (2026). Introducing the STI: a market index for the CS2 skin market. Skin Trackers. https://skintrackers.com/en/blog/introducing-sti-cs2-skin-market-index

Jorgin Fernandes, "Introducing the STI: a market index for the CS2 skin market," Skin Trackers, 2026, https://skintrackers.com/en/blog/introducing-sti-cs2-skin-market-index.

@misc{skintrackers_introducing-sti-cs2-skin-market-index,
  author = {Jorgin Fernandes},
  title  = {Introducing the STI: a market index for the CS2 skin market},
  year   = {2026},
  url    = {https://skintrackers.com/en/blog/introducing-sti-cs2-skin-market-index},
  publisher = {Skin Trackers}
}

https://skintrackers.com/en/blog/introducing-sti-cs2-skin-market-index

Disclosure: Methodology is public at /en/methodology and the data API at /api/indices. Skin Trackers is editorial — no marketplace, no commission, no conflict of interest with any specific skin or buyer/seller. The 6-year backtest reflects the 2020-2026 window; the next window will look different.