What the study found
The study found a long-term convergence in global tariffs, meaning countries with higher starting tariffs tended to reduce them faster over time. It also found a post-2018 divergence led by the United States, which broke the earlier pattern of alignment.
Why the authors say this matters
The authors suggest these findings point to an important structural shift in global tariff policy and to growing fragility in trade alignment. They also conclude that the results are relevant for understanding the resilience and governance of the multilateral trading system, including the WTO, the World Trade Organization.
What the researchers tested
The researchers analyzed a balanced panel for the United States, China, Japan, the European Union, and the world average from 1990 to 2020. They used ß-convergence tests, which assess whether higher-tariff economies reduced tariffs faster, s-convergence tests, which measure whether differences across countries narrowed, structural break analysis using Quandt–Andrews unknown breakpoint tests, and a difference-in-differences model with Driscoll–Kraay standard errors.
What worked and what didn't
The ß-convergence results showed that countries with initially higher protection levels reduced tariffs more rapidly. The s-convergence analysis showed a steady decline in cross-country tariff dispersion, although the pace slowed after the 2000s. Structural breaks were identified in the European Union in 1993, Japan in 1995, and China in 1994 and 2001, while the United States showed clear divergence after 2018; the difference-in-differences estimates indicated that U.S. tariffs rose significantly relative to other economies.
What to keep in mind
The tariff data end in 2020, so the analysis does not fully cover the final phase of the Trump administration's protectionist measures or the trade disruptions associated with COVID-19. The study also focuses only on tariff indicators and does not include non-tariff measures.
Key points
- Global tariffs showed a long-term convergence trend from 1990 to 2020.
- Cross-country tariff dispersion declined over time, but convergence slowed after the 2000s.
- The European Union, Japan, and China had structural breaks linked to liberalization episodes.
- The United States diverged after 2018, with tariffs increasing relative to other economies.
- The analysis uses tariff data only and ends in 2020.
Disclosure
- Research title:
- Global tariffs converged long-term, then diverged after 2018 in the U.S.
- Authors:
- Nil Sirel Öztürk
- Institutions:
- Trakya University
- Publication date:
- 2026-03-29
- OpenAlex record:
- View
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