Abstract: Using fertility data from national authorities and national censuses of China，Japan，and South Korea，this study analyzes the levels and trends of mean age at childbearing ( MAC) of the three countries from 1990 to 2015. After isolating the effects of parity composition and childbearing schedule respectively by decomposition technique，the article examines quantitatively the mechanism that underlies dynamic changes and cross-national differences of MACs. Results indicate that the MAC of China experienced a decrease between 1990 and 1995，followed by a sustaining growth afterwards. The increase of MAC in China is driven by the postponement of childbearing and the changes of parity composition， with the former playing a larger role. The inherent mechanism since 2010 deserves special attention. Compared with Japan and Korea，China still has relatively lower overall and parity-specific MACs. Although all of the three countries have witnessed an increase of MAC during the past 25 years， they demonstrate different patterns in terms of the roles of parity composition and birth timing. The accuracy of MAC in identifying the timing of period fertility and the policy implications of timing on upturning fertility level are discussed.

Keywords:  Mean Age at Childbearing, Parity Composition, Fertility Postponement, Low Fertility Level, The Populations of China, Japan and South Korea

摘要： 文章描述 1990 ～2015 年间中日韩三国妇女平均生育年龄的变化特征，揭示孩次结构 和分孩次生育时间对平均生育年龄指标的影响，分析三国内部及国家间妇女平均生育年龄时期变化 与国别差异的影响机制。研究发现，观察期间中国妇女的平均生育年龄先下降后上升; 平均生育年龄 的提高是孩次减少与生育推迟共同作用的结果，后者的影响极为显著，但 21 世纪近 5 年的内在机制表现值得关注。与日韩相比，中国妇女总体及分孩次的平均生育年龄都相对偏低; 三国妇女的平均生 育年龄上升态势后的内在机制存在差异。文章还就平均生育年龄指标在衡量生育时间的准确性问 题，以及全面两孩政策背景下生育时间在提升生育水平方面的政策意义进行讨论。

关键词: 平均生育年龄, 孩次结构, 生育推迟, 低生育水平, 中日韩人口