Thresholds & measurement

An EconomicNexusThreshold carries more than a dollar figure:

• salesDollars, transactions, combinator — the crossing test (isMet).
• measuringPeriod — the window a state measures over (previous / current / previous-or-current calendar year, or rolling twelve months). It tells you how to accumulate the SalesLedger.
• salesBasis — which sales count (gross / retail / taxable).
• includesMarketplaceSales — whether marketplace-facilitated sales count toward the seller's own threshold.

The engine's crossing test uses the figures; the measurement dimensions are guidance for the host's accumulation, so the ledger you feed matches what each state actually measures. All of this comes from the cited us-tax-data dataset (by-section/nexus.json), a dated-window list so a pending threshold change is carried until it takes effect.