Does Fertility Stabilize At Low Levels? Evidence from Period, Cohort, and Subnational Data
NBER Working Papers · 2026 · Diane Coffey、Michael Geruso、Dean Spears、Sangita Vyas
中文摘要
国际机构和政府机构使用的许多人口预测假设，在当今的低生育率社会中，未来生育率将停止下降并大致趋于稳定。本文评估了支持生育率存在均衡点或从低水平反弹的证据。我们表明，无论是系统性的生育率反弹，还是在通常假设的任何生育率水平上存在稳定均衡点，都没有稳健证据支持。相反，在生育率已降至低水平的地区和时期，生育率往往继续下降。这一结论在多种数据来源、时期和生育率指标中均成立：联合国涵盖1950年至2023年所有国家—年份的时期总和生育率数据；人类生育率数据库（Human Fertility Database）中31个国家1935年至1975年出生队列的完成生育率数据；以及日本、印度和美国国内地区的生育率数据。既有文献记录了部分低生育率国家在2000年代初出现的生育率趋势逆转，我们解释了上述结果如何与这些文献相容。我们的发现为重新审视广泛使用的人口预测中所包含的均衡与反弹假设提供了实证依据。
Abstract
Many population projections used by international and government agencies assume that, in today's low-fertility societies, future fertility rates will stop declining and roughly stabilize. This paper assesses the evidence for an equilibrium point or rebound from low levels. We show that there is no robust evidence for a systematic fertility rebound, or for a stable equilibrium point at any fertility level conventionally assumed. Instead, where and when fertility has fallen low, it has tended to keep falling. This is true across a range of data sources, time periods, and fertility measures: United Nations data on period total fertility rates for all country-years from 1950 to 2023; Human Fertility Database data on completed fertility for cohorts born between 1935 and 1975 in 31 countries; and fertility rates in subnational geographies in Japan, India, and the United States. We reconcile these results with a prior literature that documented fertility reversals among some low-fertility countries in the early 2000s. Our findings provide an empirical basis for re-examining the equilibrium and rebound assumptions embedded in widely used population projections.