The Impact of Group Size and Kinship on Institutionalised Collective Action: Evidence from Pastoral Communities in the Qinghai-Tibet Plateau, China

Quota-based institutions have become central to addressing collective action problems in common-pool resource (CPR) management. This study examines how group size and kinship jointly influence the performance of institutionalised collective action, conceptualised as the observable manifestation of institutional fit. Drawing on survey data from 86 Joint Household Management (JHM) groups and in-depth interviews, we propose and test a theoretical framework linking group size and kinship to institutionalised collective action. Results reveal nonlinear and heterogeneous effects. Group size shows a U-shaped relationship with transaction costs and an inverted-U with trust, suggesting an optimal size range. Kinship demonstrates dual roles: in small groups, strong ties enhance trust but weaken formal enforcement; in large groups, kinship intermediaries supplement monitoring and strengthen compliance. Medium-sized groups most effectively combine social trust with institutional enforcement, achieving the highest degree of institutional fit. The study advances institutional fit theory, enriches the SES framework by incorporating kinship and trust, and identifies differentiated governance pathways for small, medium, and large groups. These findings contribute to CPR governance theory and provide practical insights for adaptive, context-specific pastoral institutions.