What the study found
The study found a long-term convergence in global tariffs, meaning countries with higher tariff levels reduced them faster over time. It also found a post-2018 divergence led by the United States, after a period in which tariff differences across countries had generally been narrowing.
Why the authors say this matters
The authors conclude that the findings point to a structural shift in global tariff policy and suggest that uncoordinated protectionism can disrupt policy alignment and increase uncertainty for global value chains. They also state that international coordination, institutional reform, and multilateral negotiation remain important for sustaining openness.
What the researchers tested
The researchers analyzed a balanced panel dataset for the USA, China, Japan, the European Union, and the world average from 1990 to 2020. They used beta-convergence and sigma-convergence tests, Quandt-Andrews structural break tests, and a difference-in-differences model, with Driscoll-Kraay standard errors to address cross-sectional dependence and serial correlation.
What worked and what didn't
Beta-convergence results showed that initially high-tariff economies reduced tariffs more rapidly. Sigma-convergence results showed a steady decline in cross-country tariff dispersion, though the pace slowed after the 2000s. Structural break tests identified liberalization episodes 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 showed US tariffs increased significantly relative to other economies.
What to keep in mind
The tariff data end in 2020, so the analysis does not fully capture the final phase of the Trump administration's protectionist measures or the broader trade disruptions caused by 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 each had identified liberalization turning points linked to institutional reforms.
- The United States diverged after 2018, with tariffs rising significantly relative to other economies.
- The dataset ends in 2020 and does not include non-tariff measures.
Disclosure
- Research title:
- Global tariffs converged long term, then diverged after 2018
- Authors:
- Nil Sirel Öztürk
- Institutions:
- Trakya University
- Publication date:
- 2026-03-29
- OpenAlex record:
- View
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