Methodology

A benchmark is only useful if it is boring: measured the same way every week, from real transactions, with its uncertainty on display. These are the rules every Residual index follows.

1. Realized transactions only

Indices are computed from realized sale prices — hammer prices at completed auctions — never asking prices, listings, or modeled estimates. If an asset didn't trade, it isn't in the index.

2. Medians, with sample sizes

The headline statistic is the median realized price per ISO week. Medians resist the outliers that dominate auction data. Every published number carries its sample size (n); segment cuts below a minimum cell size are suppressed rather than published thin.

3. Settlement lag

Auction sales settle over days. A week enters the index only after a one-week maturity lag, so it publishes once it is substantially complete rather than while it is still filling in.

4. Versioned methodology, point-in-time history

Every payload carries a methodology_version. A dated snapshot of every published series is archived at publication time, so the exact numbers shown on any past date remain retrievable. Methodology changes bump the version and are documented; they are never applied silently.

5. Disclosed revisions

When late-settling sales change a previously published week, the change is detected against the prior published payload and disclosed on the index page and in the JSON — the week, the prior value, the new value, and the change in sample. No silent restatement, ever.

6. Publication gates

Before anything publishes, an automated gate checks sample floors and week-over-week swing bounds. If the data looks wrong — a collection gap, a mix collapse — the index does not publish and an operator is alerted. A missing week is better than a wrong one.

Current limitations

The series are young. Early movements partly reflect lot-mix shifts rather than pure price change; segment medians are unadjusted for mix. A mix-adjusted series is planned and will ship under a new methodology version. Coverage details and window boundaries are stated on each index page.