Gender Income Inequality Within and Outside the State System in China, 2003–2021: An Age–Period–Cohort Analysis

Guided by Sustainable Development Goal (SDG) 5 on achieving gender equality and empowering all women and girls, our study examines the age, period, and cohort effects of gender income inequality across China’s public and private sector employment by utilizing hierarchical age–period–cohort cross-classification random-effects models (HAPC-CCREMs) and repeated cross-sectional data from the Chinese General Social Survey from 2003 to 2021 (N = 29,367). The results demonstrate the following: (1) Age effects of gender income inequality diverge between public and private sector employment. In public sector employment, inequality undergoes a progressive decline over individuals’ career spans, as age is institutionalized as a sector-specific capital and compresses inequality through seniority-based accumulation. In private sector employment, inequality follows an inverted U-shaped trend as age is marketized as a proxy for labor productivity, producing steeper inequality in individuals’ early careers and sharp declines thereafter. (2) Period effects of gender income inequality manifest significant developing differences across public and private sector employment between 2003 and 2021. In public sector employment, the state redistributive mechanism maintains inequality at a consistently low and stable level. In private sector employment, inequality fluctuates with China’s post-transition economic restructuring, expanding during rapid market growth (2003–2008), contracting amid structural upgrading (2010–2013), and rising again under deeper market integration (2015–2021). (3) Cohort effects are negligible, reflecting that mechanisms sustaining gender income inequality exhibit intergenerational continuity. These results demonstrate that institutional segmentation structures gendered income dynamics throughout the life course via distinct resource allocation mechanisms. Our study extends life course approaches to social inequality, emphasizing the role of gender-equality-oriented governance, lifecycle-spanning support mechanisms, and cross-sectoral coordination in mitigating gender disparities.