Methodology

Version labprice.v0 — how we normalize catalogue observations and the seed CAS basket index.

Not an offer to sell chemicals. FX/pack normalization is methodology-versioned and best-effort for HTML extracts. Raw snapshots are preferred over extracts.

What we archive

Public list prices, pack sizes, purity/grade, and stated lead times — normalized to CAS × grade × supplier × pack time series.

Normalization (v0)

CAS: strip spaces; hyphenated form (67-64-1).
Currency: store as observed; basket FX uses fixed stub rates until a live FX source is locked.
Pack: observed string + numeric size/unit when extractable.
Substitution: same CAS × grade × supplier across packs (methodology-versioned); v0 keeps pack series separate.
HTML extract: best-effort on simple catalogue markup; extract failure never blocks raw archive.

Change kinds

first_seen, price_changed, lead_time_changed, delisted, fetch_failed.

Basket index

lab.basket.median_price_move.v0 — median of period-over-period % list-price moves across seed basket CAS with usable observations that day. Coverage ratio = n_constituents / basket_size.

Full draft: track METHODOLOGY-DRAFT.md in the repo.