Historical Pricing Context
Where a commodity sits against its own recent range, with 25 / 50 / 75 / 90 percentile bands over a chosen lookback.
Example
You enter
- Commodity copper
- Lookback (months) 12
- Shard {source, agency, series_id, units, fetched, cadence, points}
You get
- Latest 536
- Points in window 12
- Series id WPU10250115
- Units Index 1982=100
- Fetched 2026-05-08
Checked against published worked examples from: BLS PPI / EIA / USDA NASS / FRED federal commodity series...
Details, formula, and sources
ScopeThe monthly series is modeled after the named public series (BLS PPI / EIA / USDA NASS / FRED), not copied from it, so read the magnitude and the spread rather than any single month. Reference only; no live fetch.
Formula or tableA MODELED monthly series per commodity, shaped after the named public BLS PPI / EIA / USDA NASS / FRED federal series: a maintainer-committed recent reading, a monthly drift, and a fixed seasonal pattern, materialized over the last 36 months at build time. These are not the published monthly values. Percentile bands (p25 / p50 / p75 / p90) computed via linear-interpolation type-7 quantile over a user-selected lookback window.
Source and editionModeled after mixed federal series, built at the date stamped on each shard. Series named: BLS PPI WPU* (industrial commodities); EIA PET.* / NG.* (retail fuel + city-gate gas); USDA NASS Quick Stats price-received data items (WHEAT - PRICE RECEIVED, MEASURED IN $ / BU / CORN, GRAIN - PRICE RECEIVED, MEASURED IN $ / BU / SOYBEANS - PRICE RECEIVED, MEASURED IN $ / BU) (agricultural).
Free accessThe series of record are free at bls.gov/data, eia.gov/dnav, quickstats.nass.usda.gov, fred.stlouisfed.org. Series IDs are listed verbatim on every shard so the real series can be looked up.
What governsReference only. Bundled at build time. Confirm against the publishing agency before relying on a number.
API field namescommodity, lookback_months, shard, latest, points_in_window, series_id, units, fetched
- Quantile method linear-interpolation type-7 (matches NumPy / spreadsheet defaults)Hyndman-Fan 1996
- The points are modeled anchor reading + monthly drift + fixed seasonal pattern; only the magnitude and the spread are meant to be read, never an individual monthscripts/build-data.mjs buildHistoricalShard
- No live fetch true (every datapoint is a same-origin static asset bundled at build time)spec.md no-runtime-fetch rule