Does Fertility Stabilize At Low Levels? Evidence from Period, Cohort, and Subnational Data

Diane Coffey; Michael Geruso; Dean Spears; Sangita Vyas

doi:10.3386/w35824

Does Fertility Stabilize At Low Levels? Evidence from Period, Cohort, and Subnational Data

Diane Coffey, Michael Geruso, Dean Spears & Sangita Vyas

Working Paper 35824

DOI 10.3386/w35824

Issue Date September 2026

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.

This research was supported by grant, P2CHD042849, Population Research Center, awarded to the Population Research Center at The University of Texas at Austin by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). Diane Coffey acknowledges support from a Mentored Research Scientist Development Award from the NICHD, grant number K01HD103999. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or the National Bureau of Economic Research.

Dean Spears
In the past, Dean Spears, while on leave without pay from UT-Austin, has been paid a salary as Executive Director of r.i.c.e., a doing business as name of RICE Institute, Inc, a 501(c) public charity non-profit corporation online at www.riceinstitute.org.

Separately from r.i.c.e., Dean Spears has personally been paid as a Short Term Consultant at the World Bank, as a consultant for IPFRI, and as a short-term Visiting Fellow and Lecturer at Princeton University’s Woodrow Wilson School. He has had travel funded by the Gates Foundation, the World Bank, the Royal Economic Society, and by many universities for a conference or presentation. He was paid an honorarium by McMaster University as the 2017 Labelle Lecturer in Health Economics and by Penn State University for his 2024 DeJong Lecture in demography. His AIIS book prize paid a subvention to Harper Collins for his book Where India Goes with Diane Coffey, for which Spears and Coffey waived royalties. His Austin Robinson Memorial Prize resulted in a prize payment to r.i.c.e. He received author royalties from Simon and Schuster for his forthcoming book After the Spike.

This research paper received no funding and used only publicly available data. Dean Spears has received research funding from the NIH, GiveWell, the Smith Richardson Foundation, the Musk Foundation, the Bill and Melinda Gates Foundation, Founders Pledge, USAID, the IGC, Longview Philanthropy, and UT-Austin, as well as from the individual donors to r.i.c.e. No funder had any role or influence in the research process or findings. No party had the right to review this paper prior to its circulation. This paper does not necessarily reflect the views of any funder.

Sangita Vyas
CUNY Hunter College, Assistant Professor (salary).

Seminar travel reimbursement: Gates Foundation, World Bank, and several universities.

In the past, I have been paid a salary as a Research Fellow of r.i.c.e., doing business as name of RICE Institute, Inc, a 501(c) public charity non-profit corporation online at www.riceinstitute.org. I have also been paid as a Short Term Consultant at the World Bank, and as a consultant of UT Austin's Population Wellbeing Initiative.
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Diane Coffey, Michael Geruso, Dean Spears, and Sangita Vyas, "Does Fertility Stabilize At Low Levels? Evidence from Period, Cohort, and Subnational Data," NBER Working Paper 35824 (2026), https://doi.org/10.3386/w35824.

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Does Fertility Stabilize At Low Levels? Evidence from Period, Cohort, and Subnational Data

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