Middle-Income Durability and Social Sustainability in China: Evidence from Household Panel Data

Social sustainability and inclusive development require attention not only to the size of the middle-income group but also to households’ capacity to maintain middle-income status over time. This study examines which middle-income household-years in China face a higher probability of moving to low income at the next survey wave. Using household panel data from the China Family Panel Studies, the analysis follows middle-income origins at wave t to observed destinations at wave t + 1. It distinguishes the relative position within the middle-income interval, prior status switching, and maximum observed consecutive middle-income duration. The observed next-state transition sample contains 23,931 household-years, of which 28.2% move to low income. In joint models, a higher relative position and longer observed persistence are associated with lower subsequent downward-mobility risk, whereas prior switching is positively associated with risk but is less stable across waves. A descriptive three-item score shows a monotonic inverse-probability-weighted risk gradient, from 4.04% at score 0 to 50.79% at score 3. These findings describe longitudinal risk associations rather than causal effects. The study approaches social sustainability through one bounded empirical dimension, the durability of the household economic position, rather than as a comprehensive measure of social sustainability or household resilience. Middle-income expansion alone is therefore an incomplete indicator of social sustainability: assessments of middle-income consolidation should also distinguish current members’ observed histories and destination-specific risks.