The United States Fertility Database: Understanding and Monitoring Changes in Local Fertility Patterns

The level of fertility in the United States has fallen consistently since the end of the 2000s, reaching a low of 1.6 children born per woman in 2023. Maintaining the current population requires a birth rate of 2.1 children per woman, so the present birth rate implies that the United States population is shrinking. If this trend continues, it could threaten the country’s economic prosperity and the financial stability of the social security system as there will not be enough working-age adults to support an increasing older population.

It is important to understand the reasons behind the fertility decline and monitor future trends. However, research has been limited due to a lack of data. This project addresses this issue by creating a database of fertility indicators for each state and the District of Columbia for every year since 1959, and for each county since 1982.

The database is freely accessible to the scientific community and the public, helping researchers and policy makers study changes in reproductive behavior and study how local economic and social factors influence the level of fertility.

The data series created by this project provides both period- and cohort-based fertility indicators that are commonly used by demographers to study fertility patterns. The primary data sources are from the National Center for Health Statistics, which records all births occurring every year in the United States, and the Census Bureau’s annual estimates of the number of women of reproductive age.

Basic demographic techniques are used to produce state-level fertility indicators. However, these methods are not appropriate for county-level estimates due to the small populations in many counties and associated large year-to-year random fluctuations. To address this problem, the project uses a statistical model based on previous research that takes advantage of the regularity in age patterns in fertility and leverages the fact that demographic behavior typically changes very gradually over time and space.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.