THE CONSTITUTIONAL OPPORTUNITY INDEX. A Screening Instrument for Locating Adoption Windows for Constitutional Reform Full-Population Screen of 150 Sovereign States, with Preregistered Falsifiers

HIGHLIGHTS ▸ Constitutions are almost never adopted whole; they spread one mechanism at a time. National constitutions have a life expectancy of roughly nineteen years, which means several are replaced somewhere in the world every year without anyone being persuaded of anything. The practical question is therefore not which country might be convinced to rewrite its founding document, but whether a given text or provision is in the reference material of the drafting rooms that will convene regardless. ▸ A constitution can be screened against itself. The gates used here are not imported from political science. Each is entailed by a provision of the text being screened — its ratification threshold, its sovereignty clause, its federalism requirement, its arms clause. A constitutional text is a self-referential object, and its own articles determine where it can lawfully be received. No external criterion is needed to find out. ▸ Across 150 states, not one can adopt the text as written. This empty set is the paper’s principal result. It is reported rather than engineered away, and it is shown to be robust: it survives the deletion of four of the six gates individually and one thousand random perturbations of every cost parameter in the instrument. The obstacle is located in the document, not in the world. ▸ The clause that excludes almost everyone is the one with the thinnest justification. The entrenched right to bear arms is satisfied by three states in 150 — two per cent. The entrenchment of radical decentralisation is satisfied by nineteen per cent. Two provisions, both protected as eternity clauses, do virtually all the excluding, and neither is derived from the framework as tightly as the provisions they sit beside. ▸ Relaxing three clauses is worth twenty-seven countries. Moving the arms clause, the entrenchment of federalism, and the maximal reading of the sovereignty clause into a national-variant layer converts eligibility from zero states to twenty-seven — eighteen per cent of the world. The trade-off is now a number rather than an opinion, and the choice is between a document nobody can adopt and a document one state in five can. ▸ Need and adoptability pull against each other, and this is structural. Where institutional capture is deep, the amendment gate is controlled by the people the amendment would remove. The measurement that identifies where a constitution is most needed is, by the theory’s own mechanism, a measurement of where it is least adoptable. Ranking targets by need alone is guaranteed to produce the wrong list. ▸ One preregistered prediction failed, and the failure is reported first. The instrument was predicted to behave as an opportunity screen rather than a need screen. At full population it does not: the composite is dominated by the need term. The weighting is not earned by the evidence, and saying so is more useful than a defensible-looking score. ▸ The largest defect only became visible at scale. Eleven of the twenty highest-scoring states are autocracies running a constitutional process convened by the incumbent. The instrument records that a process is open; it does not record who owns it. A drafting process run by the power that capture installed is not an adoption window — it is the occupier writing the next text. A screen that cannot tell these apart will send reformers exactly where they should not go, and no small sample would have revealed it. ABSTRACT Proposals for constitutional design routinely conclude with a recommendation about where they should be adopted. Those recommendations are almost never produced by a stated procedure, and are therefore neither auditable nor falsifiable. This paper specifies such a procedure and applies it to the text that generated the question, across the sovereign population. The Constitutional Opportunity Index screens states in two stages. Stage 1 applies six boolean gates derived from the adopting text’s own provisions: whether a legal route exists to put a complete constitutional text to binding popular ratification; whether national votes reach the turnout the text requires; whether the state is free of supranational primacy and of external rights adjudication as the text’s sovereignty clause requires; whether entrenched sub-national units already exist, since the text makes their creation unamendable; and whether the text’s most contested substantive clause is survivable at referendum. Stage 2 scores states on three indices — Need, Opportunity, Absorbability — combined by geometric mean, so that a zero on any one is a zero overall. Need is defined as a lower bound on the Holoviceosis Index, the programme’s existing scalar measure of capture depth. Every scored component is computed by deterministic rule from a table of primary institutional attributes, so that judgement is confined to attributes auditable against primary sources rather than distributed across index values. Applied to 150 states, the screen returns no eligible state; the maximum attained is five of six gates, by three states. The result survives deletion of four of the six gates and one thousand perturbations of the closure-cost schedule. Relocating three provisions to a national-variant layer converts eligibility from zero to twenty-seven states. Two preregistered predictions are confirmed and one is refuted: the instrument does not behave as an opportunity screen, and the need term dominates the composite. An exploratory conjecture carried from earlier small-sample work is refuted outright at full population. The paper closes by identifying a specification defect visible only at scale — the Opportunity index records that a constitutional process is open without recording who convened it — and states what must be added before the instrument is used to direct effort. Keywords: constitutional design · constitutional replacement · institutional capture · Holoviceosis Index · inversion theorem · screening instrument · preregistration · sensitivity analysis · mechanism diffusion · philosophy of virtues Subject classification: Comparative Constitutional Law · Political Philosophy · Measurement Methodology · Democratic Theory