Three essays on social interactions and networks

This dissertation focuses on the social interaction with economic perspectives. This first essay tests peer effects in the workplace with piece-rate compensation. Reference groups are defined as the geographical peers in undirected networks. A series of spatial econometric models are employed to investigate the social effects. We identify and present evidence for endogenous effects (production) while find no evidence for exogenous effects (characteristics). We also find that the heterogeneity of endogenous effects depends on workers and their peers' characteristics, which is defined as conditional endogenous effects in this paper. Our results suggest that rearranging workers' seats according to their personal characteristics could lead to changes in overall productivity. From a field experiment design, the second essay studies the relation between social distance and training outcomes. We test our hypothesis through two measures: the tips shared with trainees by trainers, and the exist test results of trainees. We find that trainers share more tips to socially closer trainees, and the communications between trainers and trainees have a significant indirect effects on the number of tips shared. The productivity of trainees are also higher when they are socially closer to their trainers. The third essay discusses the identification problem in social peers effect studies. By considering the canonical linear in means model with the rank condition in simultaneous equations model, it suggests that the group structures determines the identifiablity of the desired social effects estimates. Transitive networks are not identified unless there are more information contained in the between group structures. Modifications to the conventional model are also suggested with respect to the recovery of transitive networks and potentially incomplete networks.