The Execution-Certainty Wedge: Allocation, Distribution, and the Design of Housing-Market Instruments

Sellers may accept a lower residential purchase offer when it is more likely to complete. How much aggregate buyer value must be given up to improve owner-occupier access in such a market? This paper develops an exploratory computational comparison of three allocation rules: a per-entity acquisition cap, a contention-linked fair share and a contention-triggered duty. A fixed-offer analytical condition identifies which acquisitions a proportional charge displaces. Dynamic policy rankings are evaluated in a stylised housing-market simulation. Settings chosen for common access targets are evaluated on separate simulation seeds. Near a five-percentage-point reduction in owner-occupier exits without purchase, the duty preserves aggregate buyer value. Near ten points, the fair share preserves more value than the duty. Achieved gains are reported explicitly because the rules do not match their targets exactly. Distributional weights can favour accepting larger valuation losses, while low institutional participation, ownership enforcement and seller listing responses limit the comparison. The paper also shows how a policy-dependent efficiency denominator can reverse the apparent sign of an effect, and why waiting times among successful buyers must be reported alongside unsuccessful exits. Companion New York City financing-related price gaps motivate the application but do not identify a corrective tax rate. Realised buyer value is distinguished from complete social welfare, including completion costs and renter outcomes. For details of changes between versions, see revision_notes.md.