Abstract: The disparity in social security contributions between private enterprises and state-owned enterprises is a concrete manifestation of the “fragmentation” of China's social security system, and this disparity has become a significant factor constraining the construction of a unified national market. This study examines how China's Fair Competition Review System (FCRS), aiming at dismantling administrative monopolies, affects the social security contribution gap between private enterprises and state-owned enterprises (SOEs). Using data on A-share listed firms from 2012 to 2024 and a quasi-experimental DID/DDD approach centered on the 2016 policy implementation, we find that the FCRS has significantly narrowed this gap by raising contributions from private firms relative to SOEs. The mechanisms identified are twofold: on one hand, dismantling industry monopolies improved private firms' access to credit and subsidies, easing financing constraints and incentivizing compliance; on the other hand, dismantling regional monopolies reduced local protectionism, leading to stricter enforcement of contribution collection from private firms. Robustness checks and supplementary evidence from household survey data further support these findings, highlighting the pro-welfare value of building a national unified market. This study offers empirical insights into how to promote social equity and protect workers' rights in the process of advancing the construction of a unified national market.

Key words: National Unified Market, Corporate Social Security Contributions, Fair Competition Review, Private Enterprises, State-Owned Enterprises

摘要： 民营企业与国有企业间的社保缴费差距是我国社保制度“碎片化”的具体体现,这种差异已成为制约全国统一大市场建设的重要因素。本文利用2012—2024年沪深A股上市公司数据,基于2016年出台的公平竞争审查制度构建双重差分与三重差分模型,以检验行政垄断的破除对民营企业与国有企业间社保缴费差距的影响。研究发现,公平竞争审查制度通过破除行业行政垄断与地区行政垄断,显著缩小了民营企业与国有企业间的社保缴费差距:行业层面的行政垄断破除通过提升民营企业相较于国有企业在信贷与政府补贴上的获取能力,改善了民营企业的融资约束与竞争环境,倒逼其提升社保缴费;地区层面的行政垄断破除通过规制地方保护行为,约束了地方政府对社保征收的弹性征管,进而提升了对民营企业社保的征收效率。此外,本文进一步利用中国家庭金融调查数据,从劳动者的角度验证了上述基准结果。本文为如何在推进全国统一大市场建设中促进社会公平和保障劳动者权益提供了经验证据。

关键词: 统一大市场, 社保缴费, 公平竞争审查, 民营企业, 国有企业