研討日期	2023年3月6日12:40~ 13:50
研討地點	國立臺灣大學社會科學院710會議室
主講題目 Title of the paper	Intra-group Externality and Inter-group Externality on Social Media Platforms under Uninformed Users
作者 Authors of the paper	Yan-Shu Lin, Van-Chung Dong, and Suwannajoi Suttiwan
文獻出處 Journal, vol.(issue), pp	Working paper
主講人	林燕淑教授
參加人員	黃鴻、林燕淑、彭正浩、王光正、高國峯、張瑞雲、郭文忠、許至乙、蘇家叡、Suttiwan Suwannajoi、楊雅棠、朱宣宥
摘要 Abstract of the paper	The positive intra-group externality and negative inter-group externality in nature exist in the environments of digital platforms, such as social media platforms in a two-sided market. Suppose that one side of the agents (advertisers) are informed and hold responsive beliefs, while the other side of agents are uninformed (users) and hold passive beliefs. For a monopoly platform, the platform profit is always lower under uninformed; the advertiser surplus is always higher under uninformed, but the user surplus and the social welfare are higher under uninformed only if the intra-group externality is small enough. Given a market structure for competing platforms, the platform profits are always lower under uninformed; the advertiser surplus is always higher under uninformed. Specifically for a single-homing duopoly, the user surplus and the social welfare remain unchanged. However, in the competitive bottle-neck markets, the user surplus is higher under uninformed, but the social welfare is higher under uninformed only the negative inter-group externality is small enough. With wary beliefs, irrespective of market structures, the equilibrium outcomes are always located between the interval of fully informed and uninformed users with passive beliefs.