The continuous decline in the number of births in China has caused extensive attention. Based on the 2017 China Fertility Survey data and from a cohort perspective, this study calculated the age-specific childlessness proportion and age-specific average number of children ever born (CEB) by birth cohort, analysed the fertility postponement and recuperation by birth order, and used decomposition methods to explore the effect of changes in age-parity-specific progression ratio, changes in the urban-rural population structure and educational structure, on total changes in the childlessness proportion and the average number of CEB at given ages between cohorts. 

The results show that the childlessness proportion by age 29 increased across cohorts and the average number of CEB by age 29 declined. The rise in childlessness proportion is more significant among urban, highly educated women, whereas the decline in the number of CEB is more pronounced among rural, less-educated women. 

The higher the age at first marriage, the higher the childlessness proportion and the lower the number of CEB by a specific age. The extent of fertility postponement increased among women in later birth cohorts, while the recuperation at later reproductive ages weakened. The decomposition results show that the decline in the number of first and second births in later birth cohorts is primarily driven by the decrease in the progression ratio to first birth at younger reproductive ages. The increase in childlessness proportion across cohorts is primarily driven by the decline in the fertility level of first births, and this effect becomes more pronounced in later birth cohorts. 

The decrease in the average number of CEB among later birth cohorts is largely driven by the effect of changes in urban-rural population structure and the effect of changes in the educational structure of women. The later the birth cohort, the greater the effect of the increasing education on the decrease in the average number of CEB. Among women with higher education, the effect of the decrease in the progression to first births on the decline in the average number of CEB is greater over time.  

Tian Wang is a PhD candidate at the Institute for Population and Development Studies, Xi'an Jiaotong University, China. She is currently a visiting PhD student at the School of Demography, Australian National University. Her research mainly focuses on low fertility level in China.