Importers of HS 3907.40 (polycarbonates) from Korea, South actually paid 10.57% on the taxed portion of the value in 2026-06 — 10.57% across everything shipped, taxed or not. Measured from official duty receipts, not the rulebook: the statutory MFN base rate on this code is 5.8%. Over the window the rate on the taxed portion moved 5.8% → 10.57%, with the largest single step -4.6pp in 2026-03. Measured from official US duty receipts · as-of 2026-06 · confidence: measured, not modelled. The HTS base rate is 5.8% — importers actually paid 10.57%, so the trade-war overlay added 4.8 pts, measured at the border (not a summed rulebook estimate). Reproduce exactly: tariff_story(hs: "3907.40", origin: "Korea, South") · see it at trimtabist.com/tariffs
HS 3907.40. The schedule base rate is 5.8%; importers from South Korea actually paid 10.57% on the dutiable value in 2026-06 — the trade-war overlay added 4.8 points, measured at the border. Measured, not modelled.
Over the window the collected rate moved 5.8% (2023-07) → 10.57% (2026-06), largest single step -4.6pp in 2026-03.
Korea, South's lower duty (10.57% vs 40.8%) lets it price up to 27.3% above China at the factory and still match on duty-inclusive customs cost. But on the LATEST measured prices, China actually lands cheaper — $2.77/kg vs $2.86/kg (duty in, freight out).
All goods from South Korea · the whole tariff ledger · reproduce: tariff_story(hs: "3907.40", origin: "South Korea") via /connect. Not customs or legal advice.