Abstract: Low fertility is a multifaceted issue and this paper proposes a demographic framework to reexamine low fertility in China. Fertility behavior is achieved through three nested conditions: women of childbearing age, entry into marriage, and childbearing within marriage. The sharp decline and the aging of women of childbearing age are direct causes of low fertility. Delayed and less accessible marriage further reduces fertility potential. Even entering marriage but not having children reduces fertility. Based on the perspective of dynamic structural differences, this study standardizes and decomposes crude birth rates using three key factors. The findings reveal that the decline in the proportion of married women has the greatest suppressive effect on fertility in recent ten years, the inhibitory impact of the size and structure of the childbearing-age women is intensifying, and the effect of marital fertility rates has shifted from positive to negative. The paper also hypothesizes future trends in these three factors and projects China's birth numbers and birth rates for 2021-2035, aiming to provide a comprehensive understanding of low fertility and inform targeted policy interventions.

BACKGROUND

In 2022, China’s population growth underwent a fundamental shift as the crude birth rate fell below the crude death rate, which marks the onset of negative population growth. By 2023, the natural population growth rate declined further from -0.60‰ in 2022 to -1.48‰, deepening the negative growth trend. The long-term low fertility levels have been the primary driver of negative population growth in China. These demographic trends prompt the government to introduce a series of policy measures to address the fertility crisis. Beyond policy concerns, low fertility has emerged as both a focal point of academic debate and a pressing societal issue.

OBJECTIVE

Unlike previous studies that primarily use the Total Fertility Rate (TFR) to assess fertility levels, we employ the Crude Birth Rate (CBR) as the key indicator. We adopt a demographic perspective to reanalyze China’s low fertility levels through the lens of dynamic structural differences. The perspective integrates temporal changes in demographic factors with spatial structural variations. It not only examines the structural determinants of fertility levels but also emphasizes the trends over time. Building on prior literature, this study proposes a systematic demographic framework that conceptualizes fertility outcomes as a sequential realization of three conditions: (1) being a woman of childbearing age, (2) entering marriage, and (3) having children within marriage. Based on this framework, we decompose and project China’s low fertility levels.

METHODS

The study uses data from the Sixth (2010) and Seventh (2020) National Population Censuses, the 1% National Population Sample Survey (2015), and the China Population and Employment Statistical Yearbook 2023. The research proceeds in three steps. First, the original data is adjusted using the Seventh National Population Census. Second, the proposed demographic framework is applied to examine changes in the number and structure of women of childbearing age, marital status, and fertility within marriage from 2010 to 2020. A three-factor decomposition of the CBR is then conducted. Finally, based on the three-factor decomposition results and assumptions about future trends in these factors, this study estimates and projects China’s birth population and birth rate from 2021 to 2035.

RESULTS

First, the decline in the number of women of childbearing age and the aging of this group are direct causes of low fertility rates. As population aging accelerates and birth rates decrease, the substantial decline in China’s population of women of childbearing age, particularly the proportion of women in their peak fertility years, has led to an overall decline in fertility rates. Second, marriage formation has become increasingly delayed and selective. The average age at first marriage in China has risen rapidly, reaching 29.38 years for men and 27.95 years for women in 2020. Beyond marriage postponement, non-marriage rates have increased across birth cohorts. Given that marriage remains a prerequisite for childbirth in China, delays and declines in marriage rates substantially reduce fertility potential. Third, fertility within marriage remains relatively stable. Although marital fertility rates decrease with age, the decline follows a pattern of rapid initial reduction that slows over time. The results of decomposition show that between 2010 and 2015, the decline in CBR was primarily driven by reductions in the number of childbearing-age women and the proportion of married individuals, while marital fertility contributed a slight positive effect. However, between 2015 and 2020, all three factors exerted downward pressure on birth rates, and marriage rates become the dominant suppressive force. Projections based on historical trends indicate that China’s birth numbers and birth rates will continue to decline, which is a trend unlikely to be reversed.

CONCLUSIONS

Fertility behavior is achieved through three nested conditions: women of childbearing age, entry into marriage, and childbearing within marriage. The sharp decline and the aging of women of childbearing age are direct causes of low fertility. Delayed and less accessible marriage further reduces fertility potential. Even entering marriage but not having children reduces fertility. The decline in the proportion of married women has the greatest suppressive effect on fertility in recent ten years, the inhibitory impact of the size and structure of the childbearing-age women is intensifying, and the effect of marital fertility rates has shifted from positive to negative.

CONTRIBUTION

Low fertility is a multifaceted issue that demands a comprehensive analytical framework. By adopting a demographic approach, this study identifies the key determinants of low fertility and integrates structural differences with dynamic change perspectives to provide a systematic explanation. This framework not only advances theoretical understanding of fertility decline but also offers valuable insights for empirical research and policy formulation.