技术赋能、用户规模与共享经济社会福利

以Airbnb和Uber为代表的共享经济业态已成为学术界关注热点，但当前研究侧重于商业模式，而忽视了凸显其"普惠"本质的社会福利分析。基于共享经济市场结构演进的三个典型阶段，本文构建理论模型刻画了技术赋能、用户规模与社会福利之间的内在关系。研究发现：在起步阶段，市场处于局部垄断状态，此时共享经济社会福利存在损失，且福利水平主要取决于技术赋能；在发展阶段，各个共享经济平台的市场范围产生重叠，平台企业间扩张用户规模的竞争将提升社会福利；在成熟阶段，平台间并购而形成"竞争性垄断"市场结构，此时社会福利可能再次得到提升。进一步的模型分析揭示了其内在机理：技术赋能对社会福利具有"替代"和"挖掘"的双重效应，而用户规模则对社会福利产生了"正负"两方面的外部性影响。本文为共享经济的平台战略和政府规制提供了有益指导。

Technology Empowerment,User Scale and the Social Welfare of Sharing Economy

The sharing economy represented by Airbnb and Uber has become a hot topic in academia, but the current research focuses on the business model, ignoring the social welfare analysis that highlights its "Pratt & Whitney" nature. Drawing upon the conceptual idea "Being not in use is not different from being wasted," it is held that every transaction in sharing economy market is a manifestation of Pareto Improvement, and a theoretical analysis is conducted in terms of the factors affecting the quantity and measure of social welfare. Furthermore, upon this analytical foundation, the paradigmatic models concerning the market structure are summarized and extracted, which characterize the three consecutive developmental stages of the sharing economy. In the meantime, some mathematical modules are constructed to delineate the intrinsic relationships among technology empowerment, user scale and social welfare regarding different developmental stages of the sharing economy. The result shows that:at the initial stage, the market is in a state of local monopoly, at this time the loss of economic and social welfare is manifest, and the level of welfare depends mainly on the technical empowerment; at the developmental stage, with the market areas of the sharing economy platforms overlapping, user-scale expansion competition will enhance social welfare; at the mature stage, featuring the merger and acquisition among platforms and the formation of "competitive monopoly" market structure, the social welfare may be boosted again. Further model analysis reveals its internal mechanism:technology has the dual effect of "substitution" and "excavation" on social welfare, while user scale exerts positive and negative external effects on social welfare. A useful guidance is offered to the platform strategy and government regulation of sharing economy.