【ポスター報告】小山拳志さん（OSIPP博士前期課程）

OSIPP博士前期課程2年次の小山拳志さんが、2026年9月12日に大東文化大学で開催された日本経済学会 秋季大会においてポスター報告を行いました。

＜報告論文＞
Title: “State-Contingent Pricing for Congestible Public Services: Evidence from Ambulance Policy in Japan”
Author: 小山拳志、沖朋香、須佐大樹、高橋佑汰
Abstract: Open-access yet capacity-constrained public services pose a screening problem: discouraging low-value demand without deterring users in genuine need. We provide causal evidence on an ex-post state-contingent user fee using a 2024 reform of ambulance transport in Matsusaka District, Japan. Under the reform, transported patients are charged 7,700 yen (about US$50) only if the attending physician determines that hospitalization is unnecessary. Using individual-level ambulance transport records and the Synthetic Difference-in-Differences, we estimate that ambulance transports fell by 13.7% (about 180 patients per month) after the fee took effect, with the decline concentrated among mild cases not requiring hospitalization and no detectable effect among moderate or severe-or-worse cases. To interpret the estimated policy effect, we develop a model of emergency call decisions under uncertainty and congestion that clarifies why retrospective, diagnosis-based pricing selectively deters low-severity demand while limiting deterrence for high-severity cases. Consistent with the implication of reduced congestion, we also find that hospital handover time (the time from arrival at the hospital to transfer of care to physicians) declined. Our findings suggest that ex-post state-contingent pricing can be a practical screening device for managing congestion in open-access public services when need is directly verified after use.