Navigating EU enlargement

The report identifies 27 factors across four themes—EU internal dynamics, expected effects of enlargement, attitudes/norms/perceptions, and external factors—that influence EU accession decisions. It argues that while the process is formally merit-based, EU actors exercise significant discretion, with normative factors dominating early candidacy and economic or political interests predominating during later negotiations. The analysis highlights how these factors varied across the 'Big Bang' (2004), 'Coda' (2007), and Croatia (2013) rounds, and provides forecasts for the 'Trio' of Ukraine, Moldova, and Georgia.

• The EU enlargement process is formally merit-based, requiring candidates to meet the Copenhagen criteria, but in practice, EU actors maintain significant discretion over the pace and outcome of accession.
• The report identifies 27 factors influencing accession, categorized into four themes: EU internal dynamics, expected effects of enlargement, attitudes, norms and perceptions, and external factors.
• Normative and value-based factors are most influential at the start of the accession process, while economic concerns and intra-EU political dynamics become more prominent during later negotiations.
• The requirement for unanimity in the European Council allows any single member state to act as a significant barrier by vetoing a candidate's progress.
• The 'Big Bang' enlargement was strongly driven by normative factors, specifically the ideal of a unified Europe and solidarity following the end of the Cold War.
• The 'Coda' enlargement (Bulgaria and Romania) is viewed as having occurred before formal criteria were fully met, which subsequently led to stricter requirements and a more rigorous process for Croatia's accession.
• The Russian invasion of Ukraine in 2022 acted as a primary facilitator for the rapid granting of candidacy to Ukraine, Moldova, Georgia, and Bosnia and Herzegovina.
• Concerns regarding 'absorption capacity'—the EU's ability to integrate new members without compromising its own functioning—serve as a primary barrier to enlargement.
• For the 'Trio' of candidates, the report predicts that Ukraine may face barriers related to its large population and agricultural sector, while Georgia's process may be complicated by its close connection to Russia and territorial disputes.

APA

Gerhalter, J., Revazishvili, K., & Padegimas, B. (2025). Navigating EU enlargement. Stockholm Environment Institute. https://www.sei.org/wp-content/uploads/2025/12/eu-accession-factors-sei2025-057.pdf

Chicago

Gerhalter, Judith, Khatia Revazishvili, and Bernardas Padegimas. Navigating EU enlargement. Stockholm Environment Institute, 2025. https://www.sei.org/wp-content/uploads/2025/12/eu-accession-factors-sei2025-057.pdf.

Wikipedia

{{cite report |last1=Gerhalter |first1=Judith |last2=Revazishvili |first2=Khatia |last3=Padegimas |first3=Bernardas |title=Navigating EU enlargement |publisher=Stockholm Environment Institute |date=December 2025 |url=https://www.sei.org/wp-content/uploads/2025/12/eu-accession-factors-sei2025-057.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{gerhalter2025navigating, author = {Gerhalter, Judith and Revazishvili, Khatia and Padegimas, Bernardas}, title = {{Navigating EU enlargement}}, institution = {Stockholm Environment Institute}, year = {2025}, month = dec, url = {https://www.sei.org/wp-content/uploads/2025/12/eu-accession-factors-sei2025-057.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }