Development and Diffusion of the Social Capital Index (SoCI)

Social capital influences community disaster preparedness, response, and recovery. In 2020, Kyne and Aldrich introduced the Social Capital Index (SoCI), a pioneering, publicly available county-level measure capturing bonding, bridging, and linking social capital across the United States. Since then, the SoCI has been widely adopted across disciplines and applied in diverse research contexts. Five years later, emerging theoretical developments and expanded data availability offer an opportunity to reassess its diffusion and strengthen its methodological foundations. This study addresses three objectives: (1) revisiting the conceptual roots that informed the original index, (2) examining its diffusion through citation and co-citation analyses of published literature, and (3) updating and extending its measurement framework using 2022 data. The results show that theories of bonding, bridging, and linking social capital shaped the index’s design; that the SoCI has diffused across environmental science, public administration, geography, public health, and sociology; and that expanding the index from 19 to 26 indicators enhances its theoretical alignment and empirical coverage. These updates improve the SoCI’s ability to complement existing indicators and deepen understanding of relational capacity, vulnerability, and resilience across U.S. counties.