Chinese National Identity, Social Capital and Common Prosperity in Ethnic Minority Regions—A Moderated Mediation Test Based on Interethnic Interaction, Exchange and Integration

Abstract Common prosperity in ethnic minority regions requires not only material accumulation but also the cohesive support of identity bonds. Through what social mechanism is Chinese national identity translated into perceptible development outcomes, and under what conditions does this transformation proceed more smoothly? Drawing on 1,916 respondents from eight ethnic minority provinces and autonomous regions in the 2023 Chinese Social Survey (CSS), this study estimates a moderated mediation model of “Chinese national identity (CNI)—social capital—common prosperity.” Stronger CNI significantly enhances common prosperity; social capital performs the principal transmission function, accounting for about 80% of the total effect; interethnic interaction, exchange and integration (IIEI) moderate both stages of the transmission chain, with the conditional indirect effect increasing in the level of IIEI; quantile regressions show that social capital follows a “charcoal-in-the-snow” pattern—providing critical support where it is most needed—in less prosperous regions, whereas CNI and IIEI follow an “icing-on-the-cake” pattern in more prosperous ones; and a 2021 cross-temporal replication confirms the stability of the chain. These findings clarify how identity cohesion is converted into development performance, offering a reference for multi-ethnic states pursuing inclusive development.