中文摘要
公私合作（PPP）医疗保险计划被视为一种有望在维持财政可持续性的同时扩大保障覆盖面的工具。然而，在中国这样已实现基本公共医疗保险全民覆盖、但私人保险市场仍处于新兴阶段的环境中，人们对其影响知之甚少，尤其不清楚此类计划究竟是提高了总体覆盖率，还是挤出了现有的私人保险。为考察这一问题，我们利用中国城市定制型补充医疗保险（CCSMI）在各城市间交错推出的时点差异，并结合一套新颖的私人健康保险交易层面数据。结果显示，CCSMI在广延边际和集约边际上均存在显著的溢出效应：它大幅挤出了私人保险购买，并降低了平均保障金额。消费者支付的平均保费也随之下降，其中三分之二的降幅源于消费者转而选择保障范围更窄的产品，其余降幅可能源于保险公司的定价调整。粗略估算表明，私人保险购买量的下降至少抵消了CCSMI参保增量的25%。这些发现为全面评估公私合作保险项目提供了重要启示。（JEL分类号：I13、H42、G22、G41）
Abstract
Public-private partnership (PPP) health insurance plans have been viewed as a promising tool to expand coverage while maintaining fiscal sustainability. However, in settings like China, with universal basic public insurance but still-emerging private insurance markets, little is known about their impact, particularly whether they increase overall coverage or displace existing private insurance. To examine this, we leverage the staggered introduction of China's City-Customized Supplemental Medical Insurance (CCSMI) across cities and a novel transaction-level dataset of private health insurance. Results reveal significant spillover effects on both the extensive and intensive margins: CCSMI substantially crowds out private insurance purchases and reduces average coverage amounts. Average premiums paid also decline, with two-thirds of the reduction driven by consumers opting for narrower coverage and the remainder likely due to insurers' pricing adjustments. A back-of-the-envelope calculation suggests that the decline in private insurance purchases offsets at least 25% of CCSMI enrollment gains. These findings provide important insights for comprehensively evaluating PPP insurance programs. (JEL I13, H42, G22, G41)