Abstract: Although education return has always been a hot topic in Chinese sociology， most of the existing studies focus on exploring causal relationships and heterogeneous effects in individual life courses， and efforts to track the long-term trend at the macro-level remain scarce. Using pooled samples comprising 12 waves of data from the CGSS surveys between 2003 and 2021， we analyse the trends in earnings at different education levels in China over the last two decades and examine whether the economic returns to higher education have experienced a significant decline.
Using high school graduates as the reference group， the study first measures the differences in economic returns of different education levels relative to the high school-educated population and presents the trend of change over the last two decades. Next， we employ the factor decomposition framework to assess the impact of long-term changes in five dimensions of social structural factors， such as market environment on the economic returns of different education levels. The results show that， with the exception of the postgraduate group， the overall economic returns for all education levels have remained in a relatively stable range over the last two decades. By controlling for social structural factors at the 2021 level for each wave， we find that long-term changes in social structure have increased the income advantage of the higher educated people relative to high-school population on the one hand， but have narrowed the income gap between groups in other educational levels on the other hand. By analysing the birth cohorts of the samples， we also find that the economic returns to higher education are significantly higher for the 1950s and 1960s birth cohorts than for those born after 1970， but the economic returns to higher education remain relatively stable between the 1970s and 1990s birth cohorts. With the expansion of higher education， changes in structural factors such as the increase of high-level jobs have contributed to the relative stability or slight increase of economic returns to higher education in China.

Key words: education return, longitudinal trend tracking, social structural change, decomposition framework, counterfactual scenario