The Effect of Social Media Information on College Major Choices in China: A Difference-in-Differences Analysis

The choice of a college major is a critical decision for millions of students in China, yet it is often made under conditions of significant information asymmetry. The recent rise of social media has introduced influential, unregulated actors into this high-stakes environment. This study provides a large-scale causal analysis of a social media information shock on college major choices in China. Leveraging the "Zhang Xuefeng Phenomenon", an event where a prominent influencer vehemently discouraged Journalism and Communication majors, as a natural experiment, we employ a difference-in-differences (DID) design on a comprehensive dataset of university admission ranks from 2017 to 2023, covering over 3.3 million observations. Our findings reveal that the influencer's negative signal caused the admission rank for Journalism and Communication to worsen by a substantial 13.1% across all institutions and by 24.7% at elite "Double First-Class Initiative" universities. A significant asymmetric response is identified: this negative impact was nearly double the magnitude of the positive effect observed for the endorsed Computer Science major, suggesting student decisions are driven more by risk aversion than by the pursuit of opportunity. The influencer's pragmatic, employment-focused ideology also generated positive spillover effects, boosting the popularity of related fields, such as transportation. Furthermore, a triple-difference (DDD) analysis shows the shock's impact was significantly weaker in provinces with higher per capita GDP, indicating that stronger local economic contexts can buffer against centralized negative signals. This research provides robust evidence that social media influencers have become powerful new players in the educational landscape, capable of shaping national human capital flows and posing novel challenges for students, universities, and policymakers.