Methodology note — How we tag variants by size, leather, color, and hardware

This is the July 2, 2026 entry in our rotating methodology series — sixteen explainers cycling through the statistical concepts and data assumptions that sit behind every Bagonomics research piece. The series is meant to be read once and referenced often. Today's entry covers how we tag variants by size, leather, color, and hardware.

Bagonomics aggregations are computed at the variant level. A variant is defined by the combination of size, leather, color, and hardware. The Hermès Birkin 30 in Togo leather with palladium hardware in noir is one variant. The same size in Togo in noir with gold hardware is a different variant. The same size in Epsom leather in noir with palladium is also a different variant. These distinctions matter for pricing — a Birkin 30 in standard configurations can have a thousand-dollar median spread between two hardware tones — and they have to be encoded consistently.

Our variant taxonomy is hand-curated for the brands and models in coverage. Each variant has a stable slug, a canonical descriptor combining the four dimension values, and a reference to the parent model. When a new sale lands in our pipeline, the tagging step matches the sale against the canonical variant; un-matchable sales are routed to a manual-review queue rather than dropped or mis-attributed.

Size is the easiest dimension. Manufacturers publish size labels consistently and the size shows up in seller listings as a clearly identifiable token. The Birkin comes in 25, 30, 35; the Kelly in 25, 28, 32, 35; the Chanel Classic Flap in small, medium, large, jumbo, maxi. We use the manufacturer's own size labels as the canonical form.

Leather is harder. The same leather can be referred to by different names on different platforms. Hermès Togo is sometimes listed as "togo" and sometimes as "Togo Calfskin" and sometimes as "soft grained calf." Our tagging step normalizes these synonyms against a per-brand leather glossary. We maintain the glossary by hand because new leathers appear faster than any rule-based tagger could keep up with.

Color follows a similar logic. Hermès has a published color palette with names; resellers sometimes use the official name, sometimes a translated name, sometimes a descriptive substitute. We match against the official palette where it exists and against our own normalized palette where the brand does not publish one.

Hardware splits cleanly into palladium versus gold versus brand-specific variants like ruthenium or rose gold. Palladium and silver are sometimes used interchangeably by sellers; the actual hardware on a Hermès bag is palladium, and we tag it as such regardless of which token the listing used.

What we do not separately tag at the variant level is condition. Condition is recorded at the transaction level, not the variant level, because the same physical bag can change condition over its lifespan and the same variant can be sold at any condition state. Variant medians are computed across all conditions; we publish conditional medians at the transaction-level deep-dive pages where the sample supports it.

We also do not tag year-of-production at the variant level. Year-of-production is a transaction attribute that we capture where the seller surfaces it; cohort analysis is published as a separate cut. The variant is the cross-section dimension; the cohort is the time dimension.

The reason for this discipline is the comparability guarantee. When we say the Birkin 30 in Togo noir with palladium has a 90-day median of a certain dollar amount, that number is a like-for-like read across every transaction in the window. No mixing of leathers, no mixing of hardware tones, no mixing of colors. The variant is the unit at which the market actually clears, and the variant taxonomy makes the aggregation honest.

Where this comes up in our research

This concept anchors a number of Bagonomics analyses. The research archive surfaces the live applications; the methodology hub collects the full set of these notes for sequential reading.

Methodology

Part of the Bagonomics daily editorial rotation — a 14-day cycle of daily research pieces. Each day's slot is selected from the rotation by day-of-year so the same calendar date always lands on the same topic. Data is frozen at publication; live numbers are visible on the linked entity pages. Methodology notes are editorial explainers — they do not contain time-varying computations and the body text is stable across reruns. The slug rotates by date so that each calendar day in the cycle has its own URL, keeping the daily-publication cadence intact.

*Snapshot frozen at publication. Daily editorial rotation — see /research for the full archive. This is statistical analysis, not investment advice.*