How do changes in import volumes and tariff rates explain year-over-year revenue shifts from 2015–2025?
Executive summary
Changes in effective tariff rates in 2025 drove large, observable increases in customs revenue: Penn Wharton estimates tariff changes raised $101.2 billion between January and August 2025 [1], Yale’s Budget Lab counts about $146 billion in total net customs duty revenues in 2025 through August [2], and several trackers and agencies report the average effective tariff rate jumping from roughly 2–2.5% at the start of 2025 to double‑digit levels by mid‑2025 [2] [3] [4]. Import volumes moved unevenly across sectors—some industries saw sharp declines while overall imports rose in early 2025—so revenues reflect a mix of higher rates, compositional shifts, and importer behavior [5] [2].
1. Big‑rate changes, big headline revenue effects
Multiple independent analyses show that the policy shift in 2025—large, frequent tariff rate increases—was the proximate cause of large revenue gains: Penn Wharton tallied $101.2 billion from tariff rate changes in Jan–Aug 2025 [1] while Yale’s Budget Lab reports $146 billion in net customs duties through August 2025 [2]. The Congressional Budget Office and other modelers quantify the average effective tariff rate rising by roughly 14–15 percentage points relative to 2024 policy, bringing the overall AETR into the mid‑teens and the highest levels since the 1930s by some measures [3] [4].
2. Import volumes did not fall uniformly; sectoral composition mattered
Higher tariffs did not translate into a universal collapse in import volumes. PIIE finds imports actually surged in the first half of 2025 overall, though certain categories like transport equipment fell sharply (real import volume for transport equipment down 19.6% April–July 2025) even as duty‑to‑import ratios rose for those sectors [5]. That uneven response means overall tariff revenue is shaped not only by headline rates but by which goods are still imported and at what values: high‑rate tariffs on large‑volume categories will raise revenue even if volumes drop modestly [5] [2].
3. Importer behavior and timing blurred year‑over‑year comparisons
Analysts emphasize that importers adjusted timing and sourcing. Penn Wharton notes importers accelerated purchases and shifted purchasing patterns, muting some revenue gains that would have occurred absent behavioral changes [1]. Yale’s Budget Lab and the CBO also model substitution and price responses—CBO assumes exporters absorb part of the tariff shock (cutting prices by about 5% of the tariff increase), which reduces import declines and raises realized revenues relative to simpler models [4] [2].
4. Effective rates versus statutory headline rates: the crucial distinction
Several sources warn that the “headline” tariff percentage is not the same as the effective tariff rate actually collected. PIIE and the Bipartisan Policy Center emphasize that exclusions, delays, and administrative adjustments lower the effective duty collected as a share of import value compared with announced statutory rates [6] [7]. Yale and Penn Wharton report effective tariff rates rising in reported data (to roughly 10–11.5% in mid‑2025 by one measure) but note statutory fully phased‑in rates are higher—so realized revenue depends on enforcement, exclusions, and importer tactics [2] [1].
5. Modeling differences produce divergent revenue forecasts
Forecast spreads are large because groups make different modeling choices. Yale’s Budget Lab and CBO diverge on the AETR and long‑run fiscal impacts—TBL estimates 15.6 percentage points pre‑substitution while CBO’s August work cited an 18‑point increase on a like‑for‑like basis—partly due to different treatments of non‑compliance, timing, and substitution [3]. These methodological choices explain why projections of multi‑year revenue effects vary from hundreds of billions to trillions [3].
6. What explains year‑over‑year revenue shifts 2015–2025 in one frame
Across the decade, tariff revenue was historically low as a share of federal receipts until 2025; the dramatic uptick in 2025 is best explained by three interacting forces found in the reporting: large statutory increases in tariff rates and broad new schedules (raising potential AETR) [3] [8], the composition and resilience of import flows—some categories and trading partners continued high‑volume shipments while others contracted [5] [9], and importer timing, price passthrough, exemptions, and enforcement which determine effective collections versus statutory exposure [1] [4] [6]. Together they produced the sharp year‑over‑year revenue rise observed in 2025 relative to prior years [2] [1].
Limitations and competing viewpoints: models disagree on the magnitude and persistence of revenue gains because they differ in assumptions about exporters’ price responses, non‑compliance, and substitution across suppliers [3] [4]. Available sources do not mention microdata for every HTS‑6 product across 2015–2025 in a single harmonized table; researchers instead combine USITC, Census, and Treasury data and reach somewhat different totals [10] [6].
Bottom line: higher statutory rates in 2025 raised the revenue ceiling; whether revenue grew year‑over‑year as much as headline numbers imply depends on shifting import volumes, sectoral composition, and administrative factors—issues highlighted by Penn Wharton, Yale’s Budget Lab, PIIE, the CBO and others in the available reporting [1] [2] [5] [4] [6].