base rate:
Only 1 country (UK) has ever formally left the EU in ~50+ years of the bloc's existence, across ~27 current members. Per-country-year base rate is roughly 0.07%. Over 3.7 years across 27 members, a naive base rate would be ~7%, but this overstates it given that Brexit itself was an extraordinary event requiring years of political buildup.
evidence updates:
Strong DOWN evidence: (1) No Article 50 notification is active in 2026 — this alone nearly precludes YES given the Brexit-length ~3 year minimum. (2) Major Eurosceptic parties (Meloni, Orbán, even RN) have moderated exit rhetoric post-Brexit, observing the economic damage. (3) Iceland moving toward joining rather than any country toward leaving reinforces the 'accession not exit' direction. (4) EU has accommodated difficult members via negotiations. Minor UP considerations: French 2027 election tail risk, Hungary rule-of-law escalation, unknown geopolitical shocks — but none credibly produce a completed exit by Jan 2030.
combination method:
Weighted average of three highly correlated sub-questions, all pointing to the same conclusion. No adjustment needed for correlation since they all measure facets of the same unlikely scenario.
final:
Combining a ~7% naive base rate with strong negative evidence (no Article 50 triggered, no referendum scheduled, moderated Eurosceptic rhetoric, EU accommodation of dissenters, time running out for Brexit-length process), I estimate ~4% probability. This accounts for tail risks (unexpected political shock, expulsion scenario, compressed timeline) while reflecting the overwhelming evidence that no exit is currently in motion.
ensemble:
{'ensemble_count': 3, 'perspectives': {'base_rate': {'p_yes': 0.04, 'confidence': 0.85}, 'evidence_driven': {'p_yes': 0.03, 'confidence': 0.88}, 'contrarian': {'p_yes': 0.04, 'confidence': 0.82}}, 'spread': 0.01, 'individual_p_yes': {'base_rate': 0.04, 'evidence_driven': 0.03, 'contrarian': 0.04}}