How this index is calculated

A sale price is never observed. Forum sellers do not publish what they accepted, and we do not infer it. Everything on this surface is what somebody asked.

The listing-ask panel is every asking price matched to a catalog reference, live or closed. The closing-ask panel is the last price a seller asked before their listing closed. A closed listing may have been withdrawn or sold, so the second is also an asking price: it reads a little high, and it serves as an independent cross-check on the first.

A post that cannot be resolved to a specific watch in the lug²lug catalog stays out of the panel at every stage. That is what makes the index a matched-model index: every price belongs to a known watch.

Older forum threads exist only where nobody pruned them, and the direction of that survivorship bias is unknown. The index is indexed to 2022 = 100 and does not extend behind it.

A year’s change is the average change across watches listed in both that year and the one before. A watch that appears for the first time this year contributes nothing to this year’s change, which is why a newly crawled brand can never move the line on arrival.

Every matched watch contributes equally regardless of price. A dollar-weighted index of this panel would be a tracker for whichever brand happens to list the most expensive watches, which is a different measurement wearing this one’s name.

Within a window, a watch’s many listings collapse to one figure per window, so a single heavily reposted listing cannot outvote the rest of the panel.

The 95% interval printed beside every figure is a bootstrap interval resampled at the level of the watch: listings of the same watch move together, and resampling listings would produce intervals several times too narrow. Extreme relatives are winsorized before the mean, and impossible ones are dropped; both counts are stored with the point.

An index level is the product of the yearly links, starting from 2022 = 100. Where a year cannot publish a link, the level chain cannot continue through it, and no level is drawn, so no gap is bridged with an assumption. That is why about a third of the cuts show a year-by-year ladder and no level line.

Every figure on this surface is annual, with no quarterly, monthly or weekly line anywhere, unlabeled sparklines included. Measured quarterly standard errors run several percentage points against quarterly moves of a few percent, so a quarterly line would be a picture of our own sampling noise.

Watches from one brand move together, so a brand cut carries much less independent information than its count suggests. That is why most brand cuts publish a range even when their panel looks large.

A watch is in the under-$500 band because of what it goes for secondhand. That is also why price-band pages carry no list of the watches in them: naming the members would publish each member’s market price, and per-watch prices are not part of this free surface.

Keying the panel by (brand, reference) was built and tested, and it does not produce a catalog-free key, so the panel stays keyed by the catalog watch.

A year-to-date reading widens its window every month, so it moves. It is marked provisional wherever it appears.

Forum listings backfill for weeks after a window shuts, so an annual figure genuinely moves for a while. A point freezes after its window has been closed long enough for that to settle. After that, a published figure that changes has to be recorded as a restatement with a reason, because the one sentence a competitor gets to say otherwise is “their 2024 number changed after we quoted it”.

Each published vintage of a point is appended to an immutable record, so what a figure said on the day it was quoted remains recoverable.

The catalog is probed nightly and the time of every probe is recorded against the watch. A row lands in the stock log only when the answer moved: at this time, this watch stopped being in stock and started being sold out, and this is how we know. A probe that finds the same state as the night before writes nothing.

Most rows come from something a storefront said: a catalog API, structured data on the product page, a meta tag, or a page idiom. Two are inferred. pdp-404 is recorded when a product page has returned 404 three nights running, and feed-vanish when a row has been missing from a catalog feed three nights running. Both are usually right, and both are late by up to three days by construction, which is precisely the interval that matters for a limited release. Every surface marks them, because a sell-out date reached this way is a floor.

Until that day the sync computed a stock change, acted on it and discarded it, in four separate places. There is no history to backfill from. A watch we had already read was written in with one anchor row dated to its last check before the log opened, and an anchor records when the clock started.

So a watch with no transitions has not been seen to change. That is the only statement the log supports, and it is worded that way everywhere it appears.

A watch was written into the log only if we had already read a stock state for it. Thousands have never returned one: a store we cannot reach, a brand with no product page we can parse, a watch that is not sold new anywhere we can see. Those watches have no anchor row and no clock, and are left out of the count of watches being watched.

That shortfall can last. A watch joins the log the first time a probe actually answers for it, and for some of them no probe ever will. The market page prints the number of watches with a clock running beside the size of the catalog, so the fraction is visible.

A brand behind a bot wall emits no events and therefore looks perfectly steady. So does a brand whose store we have not reached in a month. Nothing on this site reads a quiet history as a stable one, and the date of the last check travels with the history wherever it is shown.

The log publishes dated stock changes and nothing derived from them. Sell-out speed, restock cadence, time to restock, and any percentile built over them each need a denominator this log lacks.

No sale price is observed anywhere in this pipeline.

Per-watch annual moves are dominated by sampling noise at this panel size, measured at roughly the size of the moves themselves. No per-watch trend line is drawn anywhere on this surface. The only per-watch rates published at all are the handful whose interval clears zero, and they are labelled as such.

A matched-model index of used goods carries some drift from age alone, and that drift stays in the figure. Read a figure as what an owner holding these watches saw.

The panel is what enthusiasts list to each other, which skews to microbrands, Japanese brands and the sub-$2,000 field. Rolex carries a fraction of the matched references Seiko does here because Rolex trades mostly through dealers and auctions, outside the market we measure. Read a Rolex cut here as “what forum sellers asked”.

This is a measurement of asking prices in one corner of one hobby. Nothing here is investment advice or a recommendation to buy or sell.