The United States’ demographic situation could change during the decades of the 21st century, and signs indicate that over the longer term the country’s population dynamics may slow or even begin to decline, presenting new challenges for America’s society, economy, and political institutions.
The nation’s economic policy and immigration policy may accelerate this trend. This was the subject of a press briefing held by American Community Media with Dr. Ana Langer, Director of the Harvard Women and Health Initiative, emeritus professor at the Chan School of Public Health and the Department of Global Health and Population; Dr. Philip Cafaro, associate professor of philosophy at Colorado State University; and Anu Madgavkar, a partner at the McKinsey Global Institute.
Participants discussed the factors that may lead to negative population growth, its economic impact—including the shrinking labor force—and its potential consequences for the environment. This trend reflects a global shift already reshaping Europe and East Asia.
Two-thirds of humanity now lives in countries where fertility rates fall below the 2.1-children-per-family replacement level. Based on United Nations projections, by the year 2100, population in some major economies could fall by 20 to 50 percent. Until now, the United States has largely avoided such population decline for various reasons, but that may be coming to an end.
The American population has exhibited exceptional demographic growth globally, due in part to relatively high levels of immigration and to relatively stable population growth. According to the most recent official data and projections, however, that growth will slow over the long term and may even reverse around 2100.
According to the U.S. Census Bureau’s 2023 demographic projections, the U.S. population will grow more slowly throughout the 21st century than previously expected under current trends. According to Ana Langer, population could peak around 370 million by approximately 2080, after which the country could enter a period of slow decline.
Estimates suggest that by 2100, the population may reach around 366 million—representing only a 9.7-percent increase compared to 2022. The main drivers behind demographic trends—natural increase, mortality, and international immigration—now show new patterns.
The birth rate is on a persistently declining trajectory and remains below replacement level. The willingness to have children does not reach the so-called replacement threshold of 2.1 children per woman. This means that in the long term, the population would not be able to sustain itself naturally.
As a result—and combined with rising mortality—natural increase may fall behind deaths around 2038, meaning the number of deaths could exceed the number of live births. This demographic turning point is due to population aging: the large “baby boom” generation is reaching and passing retirement age, pushing the median age upward.
Meanwhile, the proportion of younger age groups is declining. Based on Census data, the median age in 2022 was 38.9 years, and by 2100 it is projected to be roughly 47.9 years, which means there will be more residents aged 65 or older than there will be children under 18. This aging trend is not unique to the United States—similar demographic changes have been observed across many developed nations—but it is not as rapid as what occurred in Europe or Japan.
At the same time, American demographers and sociologists point out that declining fertility and “fertility postponement”—the delay of childbearing—are increasingly common, particularly among highly educated women, which further reduces overall fertility rates.
Immigration plays a crucial role in America’s demographic dynamics. According to Census projections, during the remainder of the 21st century—in most scenarios—international immigration will be the main driver of population growth, especially if current immigration levels are maintained. These projections, however, were issued before recent changes in immigration policy.
A decline or tightening in immigration could have dramatic effects on the demographic trajectory: under the Census Bureau’s “low immigration” scenario, the population would grow only to 346 million by 2043, and then begin to shrink, reaching around 319 million by 2100—representing a clear demographic decline. Yet even this forecast may be optimistic compared to actual policy developments.
Under a scenario close to “zero immigration”—a hypothetical but illustrative outcome dependent on political decisions—U.S. population could fall to as low as 226 million by 2100 from the current roughly 340 million, meaning a two-thirds drop in population. Even if the United States does not reach that extreme, Trump-era immigration policy—through deportations, removals, and stringent immigration restrictions—could produce a decline of similar scale.
This enormous difference between immigration-based scenarios demonstrates how radically the demographic trajectory may change depending on decisions regarding America’s immigration system and the entry and settlement of asylum seekers and migrants, said Dr. Philip Cafaro, noting that the current trend is alarming.
According to the Penn Wharton Budget Model—which uses alternative demographic projections—U.S. fertility has remained below replacement level for decades, and if it remains there, population growth will stall and become low or negative even if the mortality rate improves.
Demographic trends are changing not only total population size, but the composition of the population itself. The proportions of various ethnic and origin groups will shift over the coming decades: the share of the non-Hispanic white population will decline, while the proportion of Hispanic and other ethnic groups will increase.
This in itself poses social, political, and economic challenges, as labor markets, consumer behavior, and educational systems all must adapt. Yet systemic racism could be used as justification for tightening immigration policy.
Population aging places severe burdens on healthcare and pension systems. If fewer working-age residents must support an increasing number of retirees, this places fiscal pressure on both state and federal budgets. Meanwhile, population decline or stagnation could weaken economic growth, reduce labor supply, and affect the dynamics of innovation and investment.
Overall, the United States faces 21st-century demographic challenges previously associated primarily with Europe or Asia. The slowing—or under certain scenarios, long-term decline—of America’s population is the cumulative result of low birth rates, rising mortality, and unstable immigration.
As the Census Bureau, federal budget offices, and other demographic models indicate, the future of the U.S. population is not predetermined, but highly dependent on political decisions and evolving social trends which together will shape the nation’s future. From this perspective, the rise of far-right rhetoric, anti-immigration sentiment, and racist, discriminatory, immigration-opposing government policy is deeply concerning.
