近日，北京大学市场经济研究中心特聘研究员庄晨助理教授的合作论文《Product assortment and competition: evidence from live-streaming platform influencers》在经济学领域期刊《Empirical Economics》2026年8月第71卷正式发表。

摘要：This paper examines how live-streaming influencers adjust their product strategies when competitive pressure shifts. We study the temporary suspension of Xinba, a superstar seller on the Kuaishou platform in China, as a plausibly exogenous shock to market structure. Using transaction-level data from the cosmetics market, we construct a competition index based on product assortment similarity and estimate difference-in-differences models. We find that influencers facing greater reductions in competition expanded product variety, while prices and proxies of product quality remained largely unchanged. These effects are more pronounced among influencers with higher initial exposure to the superstar. The results suggest that horizontal assortment expansion serves as the primary strategic margin of response, which is rationalized through a platform framework of low product introduction frictions and thick retail margins. By combining a machine-learning-based competition measure with conventional econometric analysis, we provide new evidence on how competition shapes product variety in emerging digital platforms.