Lower birth rates were associated with faster growth in output per working-age adult and wages over the past seven decades, according to new research. The authors found no statistically significant decline in total output, suggesting that investment and labor-saving technology may have offset part of the effect of a smaller workforce.
The finding challenges a simple assumption in demographic forecasts: fewer births today must eventually mean a weaker economy. It does not remove the fiscal and social pressures of an aging population, but it suggests that businesses and economies can adapt more than a headcount alone implies.
In Baby Busts and Growth Booms: Demographic Change and the Macroeconomy, Daron Acemoglu, David Autor, Keelan Beirne and Andrew Scott studied country data from 1950 to 2020 and local labor markets in the United States. Their paper is an NBER working paper, circulated for discussion rather than a peer-reviewed journal article.
More output per worker, not necessarily more total output
Across countries, a one-percentage-point lower birth rate in 1950 was associated with 23 log points higher GDP per working-age adult in 2020, according to the NBER’s summary of the study. The comparison uses a 20-year lag because people born in one period enter the workforce roughly two decades later.
The researchers also examined 722 US commuting zones, areas intended to approximate local labor markets. A one-percentage-point lower birth rate in 1940 was associated with about 15 log points faster age-composition-adjusted wage growth between 1960 and 2020.
Those results do not mean that a lower birth rate causes every individual worker to earn more. They describe historical relationships across large groups of countries and places. But the researchers found no statistically significant relationship between lower birth rates and aggregate GDP or aggregate earnings, even though the working-age population became smaller.
That distinction matters. GDP per worker and total GDP answer different questions. A country can become more productive per worker without increasing its total output, and governments can still face harder choices over pensions, health care and the share of adults outside the workforce.
Labor scarcity can change investment decisions
The paper’s proposed explanation is that companies respond to a scarcer supply of younger workers. Instead of treating the available workforce as fixed, employers can raise wages, invest in capital equipment and adopt technology that allows each worker to produce more.
Countries with lower birth rates in the study showed faster total-factor-productivity growth, more high-tech activity and more patenting in labor-saving fields such as automation and information technology. Total factor productivity is a measure of how efficiently an economy combines labor and capital. It can rise when a factory redesigns production so that the same workers and equipment produce more output.
The research does not show that every robot, software purchase or patent was caused by demographic change. It found patterns consistent with businesses reacting to scarcity by changing their technology and investment choices.
That mechanism connects with MBN’s earlier examination of what fewer young workers mean for business hiring and automation. Automation can ease pressure on some tasks, but it also changes the skills firms need and cannot replace every job that relies on judgement, service or maintenance.
Past adaptation is not a forecast
The authors tested several alternatives, including changes in education, female labor-force participation and the shift away from agriculture. They say those did not explain the main result as fully as the technology-and-capital response.
They also warn against treating the evidence as a prediction for the demographic changes ahead. Some countries may experience population decline and aging on a scale outside the historical experience used in the study. Technology, investment and public finances may react differently in the future.
The useful conclusion is narrower. A shrinking flow of younger workers does not automatically lock an economy into falling productivity or lower total output. The response from employers, investors and governments will help determine whether labor scarcity becomes a drag on growth or an incentive to reorganize work.
