中国出生人口的季节性模式分析

The Analysis on Birth Seasonality of China

医学及生物学研究已证实出生季节与婴幼儿发育及成年健康有着密切联系。了解季节性出生的高峰和低谷对公共健康规划和儿童疾病预防均有较大促进作用。各国存在不同的出生季节模式,目前对中国出生季节性模式的研究较少。本研究对1960年以来中国的出生季节性波动进行分析并按孩次、城乡、民族等维度进行分解。传统上中国以冬季为出生高峰,春季和夏季为出生低谷,显著不同于欧洲模式和美国模式。1990年以后由于实施计划生育政策以及妇女更广泛地使用现代避孕方法,季节性出生模式发生了变化,出生的月份偏移度随时期逐渐减弱。人们的自主控制是解释季节性变迁的关键因素。其中一孩出生的季节性最为明显和稳健,而二孩及以上孩次出生遵循不明显的季节性模式,表明二孩及以上孩次出生更多受人为选择和干预的影响。两孩政策调整后,二孩的月度分布模式发生剧烈变动,清晰地反映出人们在新生育政策环境下对自我生育计划的调适以及生育计划的实现进程。

Little research on birth seasonality has been done for China,especially for the period after the family planning policies implementation.We present an analysis of birth seasonality in China since 1960 by using various national data and demonstrate the difference between parity,residence and mother’s ethnicity.Unlike the European and American birth seasonal models,Chinese births have a significant feature of seasonality,with a peak in winter and trough in spring and summer.Since 1990,as a result of the enforcement of family planning policy and women’s use of modern methods of contraception,birth seasonal patterns have changed dramatically,and the amplitude of monthly birth deviation has gradually decreased.People’s self-control is a key factor in explaining the seasonal changes.In addition,the pronounced seasonality of first birth is robust,while the second and the third birth follows a less obvious seasonal pattern over time,indicating that higher order of births more affected by self-driven intervention related to policy.The analysis also demonstrates that the monthly distribution pattern of second child has changed dramatically after the implementation new two-child policy,clearly reflecting the adjustment of individual birth planning and childbearing within the new policy context.