The world may no longer be having enough children to replace its population. Economists Jesús Fernández-Villaverde and Patrick Norrick found that birth rates have fallen in 219 of 236 countries and territories they examined. Their research suggests that, for the first time in human history, global fertility may have dropped below the level needed for one generation to replace the next.
The trend toward lower fertility is now evident across much of the world, providing a warning about potentially significant demographic changes ahead.
They expect the global population to top out near nine billion around 2056 and fall after that. And government programs meant to encourage births, they find, hardly help. So, as people are having fewer kids, the senior demographic is expanding.
In the report titled An Aging World: 2025, which was published on August 31, the United States Census Bureau indicates that in 2025 the portion of the world’s total population aged 65+ exceeded the portion of the world’s population under the age of 5; this is a first in recorded history.
And the census projects the 65-and-older share of the global population will rise from 10.5% in 2025 to 19.6% in 2060 — close to a doubling in 35 years. And by 2060, nearly one in five people worldwide will be 65 or older, up from about one in ten today. These trends point toward a significantly older global population and warn of growing demographic pressures in the decades ahead.
America ages slowly while the world sprints
Today, according to the Census, 18.9% of the U.S. population was 65 or older in 2025, and that demographic is projected to reach 23.4% by 2060. That will move the U.S., currently the 48th oldest country of 227, to a projected 110th — not because America will get younger, but because roughly 60 other countries will get older quicker.
The oldest country, and 2060 projections
Japan is the oldest country today at 29.7% over 65. South Korea is projected to take that title by 2060 at 41% — meaning that more than two in five South Koreans will be 65+. And the percentage of 65+ in Europe will surge from 21% to 30.8%.
Further, according to the Census Bureau data, one of the primary drivers of this trend is declining fertility rates: Seventy-one percent (71%) of all inhabitants on Earth live in countries where their fertility rate is at or below replacement levels of approximately 2.1 children per woman.
The health factor and technology
Finally, one factor that often gets overlooked in discussions about an aging population is health span—not simply how long people live, but how many of those years are spent in good health. Americans may be living longer, but that does not necessarily mean they are remaining healthy for longer.
According to the U.S. Census Bureau, between 2000 and 2019, the share of remaining years that Americans age 65 and older could expect to live in full health declined by more than two percentage points. The challenge becomes even clearer when chronic illness is considered.
Data from 2016–2019 indicate that roughly 73% of Americans age 65 and older were living with at least two chronic health conditions. As the population continues to age, the growing gap between life span and health span could have major implications for health care, caregiving, the workforce, and government programs. That provides another warning about the challenges societies could face as their populations grow older.
What about potential advances in AI?
The U.S. Census Bureau’s 2060 population projections are largely based on the continuation of existing demographic trends—not on the assumption that a dramatic “longevity breakthrough” will allow Americans to live substantially longer. And while AI could eventually contribute to major advances in human longevity, its more immediate impact may be far less futuristic—and potentially just as important.
Today, AI’s greatest contribution may be helping close the gap between what modern medicine already knows and what actually happens in everyday clinical practice. That could mean detecting cancer earlier, recognizing subtle signs of disease or physical decline sooner, identifying high-risk patients before their conditions worsen, or ensuring that people who are overdue for important screenings are actually screened.
In that sense, AI may initially do more to extend health span than life span. Rather than simply adding additional years at the end of life, its near-term value could come from helping people spend more of the years they already have in better health. That distinction is especially important given the Census Bureau’s concerns about an aging population potentially spending a growing share of later life in poor health.
