PhD Oral Exam - Siming Xie, Economics

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

This thesis consists of three chapters on social networks, focusing on cultural activities and social interactions.

Chapter 2 introduces a model of friendship formation that explores whether cultural activities can help reduce segregation across racial groups. The model incorporates a bias in the matching process, where individuals engaged in the same activities are more likely to form friendships. This framework aligns with empirical findings, including increased friendships among club members and reduced segregation when students from different racial backgrounds participate equally in cultural activities.

Chapter 3 presents an empirical analysis of club participation, examining how individual decisions are shaped by social norms. The findings indicate that white students participating in basketball and black students in baseball are influenced by the size of their racial group, whereas this effect is not observed for the reverse combinations. Using a Linear-in-Mean (LIM) model, the study reveals that previous research may overestimate peer effects on individual decisions, mainly due to the endogeneity of friendship networks. The results suggest that cultural clubs play a role in fostering social cohesion across racial groups.

Chapter 4 presents a model that examines how social norms influence students' decisions to participate in clubs, highlighting a trade-off between the costs of participation and the benefits of social engagement. The model predicts that as school size increases, participation rates decline, but a higher proportion of devotee members are committed to the club. Moreover, social engagement has a stronger influence on participation decisions in larger schools. Empirical data support these predictions.