Tell Me Who You Walk With… Identification of Preferences for Socioeconomic Status and Segregation:

This article analyzes the formation of university social networks and identifies preferences for socioeconomic homophily through a model of strategic network formation. I use administrative data and physical interaction records captured by turnstiles at Universidad de los Andes (2016–2018) during the implementation of Ser Pilo Paga.
I extend De Paula’s (2018) methodological framework by incorporating classroom exposure as an individual characteristic, allowing for the modeling of how patterns of academic interaction mediate the formation of social ties. I estimate preference parameters using quadratic programming and recover identified sets consistent with pairwise stability equilibrium.
The results reveal substantial asymmetry: high-income students exhibit strong homophily, while low-income students show greater openness to diverse connections. Counterfactual simulations demonstrate that increasing the proportion of low-income students can intensify segregation in the absence of deliberate redistribution across classrooms. In contrast, a balanced classroom assignment (holding total composition constant) increases heterophilic ties.
These findings show that access policies require complementary institutional design. The architecture of exposure opportunities is just as important as demographic composition for achieving social integration goals.