{
  "name": "U.S. Manufacturing Observed Rate-Step & Import-Value Change",
  "slug": "us-manufacturing-tariff-effect",
  "version": "2.1.0",
  "url": "https://www.mfgcalcs.com/signals/tariff-effect",
  "formula": "For each family, trailing-12-month effective rate = sum(calculated duty, 12 mo) / sum(covered customs value, 12 mo). The observed rate change is the largest 12-month rise in that rate that is at least 5 pp and has a full 12-month window both before and after. Associated import-value change = (12-month customs value a full window after the step - the 12-month value before the step) / the value before x 100.",
  "customsValueVerdictBands": "customs value fell sharply <= -15%, customs value fell -15% to -5%, customs value held -5% to +5%, customs value rose > +5%.",
  "compatibility": "The CSV/JSON verdict field is deprecated wording retained for existing clients; use customsValueVerdict.",
  "unit": "percent; rate in percent, step in percentage points.",
  "source": "U.S. International Trade Commission (USITC) DataWeb per-family monthly customs value and calculated duty.",
  "provenance": "Derived entirely from USITC DataWeb, a work of the U.S. government in the public domain. Redistributable.",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "attribution": "MFG Calcs (mfgcalcs.com), compiled from USITC DataWeb open data",
  "caveats": [
    "OBSERVATIONAL, NOT CAUSAL OR A LEGAL-ACTION MATCH: the detected month is a statistical rate step, not a verified tariff effective date. Many forces (demand, exchange rates, other policy, the pandemic) moved imports over the same window. This reads co-movement, not a controlled tariff effect.",
    "The metric is declared customs VALUE, not physical volume. It combines transaction values, quantity, and product and origin mix, so it cannot identify a volume change on its own.",
    "Families whose only qualifying step is too recent to have a full settled year after it are excluded because the full comparison window is unavailable."
  ],
  "asOf": "2026-06"
}