The Chroma Collection index

A market index is the total median market value of every priceable variant inside a defined slice of the CS2 economy. CSSkinLab snapshots every index daily, so each chart point is the sum of the cross-market median price of every wear × StatTrak combination for every item in that slice on that calendar day. It's the cleanest way to track whether a category is rising, falling, or flat without watching individual skins.

For each priceable SKU in the slice, the worker takes the latest cross-market median price (filtered to entries with at least one market reporting and a snapshot from the last 24 hours), then sums those medians in cents. SKUs with stale or missing prices are excluded from the day's snapshot, which is why the SKU count moves slightly day-to-day.

Single-marketplace prices swing on small volume, and arithmetic averages get pulled around by outliers — one mispriced listing on a low-volume skin shifts the mean. The median is robust against those distortions, and pulling it from multiple marketplaces (Steam Market, Buff163, CSFloat, Skinport, DMarket) cancels out platform-specific noise. The result is a stable, comparable number across days.

Snapshots run once per day at 06:00 UTC. The chart on each detail page replays the historical snapshots; the totals shown at the top of each card use the most recent snapshot. Inter-day price movement isn't reflected — if you want minute-level prices, the per-item pages and the trade-up calculators consume the same medians at full refresh cadence.

Souvenir skins are excluded entirely from every index because they live in a separate, low-liquidity sub-market. The Cases index includes weapon cases only — souvenir packages, sticker capsules, autograph capsules, and Armory boxes are intentionally out. SKUs without a recent cross-market median (no marketplace reporting in the last 24 hours) are also dropped from that day's total so the chart doesn't drift on stale data.

ALL_ITEMS sums every priceable variant in the catalog — the broad market. The categorical indexes (Knives, Gloves, Cases, Stickers, Agents, Charms, Patches) each sum only their slice. Because of overlap rules and exclusions they don't add up to ALL_ITEMS exactly: ALL_ITEMS also covers regular weapon skins, music kits, and other priceable items that don't have their own top-level index yet.

Each CS2 collection (e.g. The Mirage Collection, The Train 2025 Collection) gets its own daily index that sums every priceable variant of every skin in that collection. STICKER_SLAB items are excluded so the index reflects skin float-and-wear permutations rather than sticker capsule contents. Collections without any priceable SKU on a given day produce no snapshot for that day — gaps in the chart are real, not bugs.

Each delta compares today's snapshot against the snapshot from N days ago — 1 day for the D delta, 7 days for W, 30 days for M. The percentage is `(today − thenAgo) / thenAgo`. If that historical snapshot doesn't exist (e.g. for a brand-new collection), the corresponding delta renders as `—` instead of a misleading zero.

Yes — that's the explicit purpose. ALL_ITEMS gives you a broad-market trendline. The categorical indexes show whether knives, cases, or stickers are leading or lagging. Collection indexes are useful for spotting capsule-driven moves (a recent operation pushing one collection up while everything else flatlines). The 30D / 90D / 1Y / All toggle on each chart lets you frame the time window you care about.

Either no SKU in that collection has a fresh cross-market median (every skin is below the minimum-marketplace threshold or stale beyond 24 hours), or the collection only contains items the index excludes (souvenirs, sticker slabs). New collections also take one daily aggregation cycle — the 06:00 UTC run — to appear. If a previously populated collection drops to $0, it's almost always a temporary price-feed gap that resolves on the next run.