How the United States Keeps Growing While Its Peers Shrink

By the populationclock.org team · Published September 28, 2026 · All figures: UN World Population Prospects 2024, medium variant

The number, and how thin the growth is

The United States holds about 348 million people in 2026 and is projected to reach 421 million by 2100, a gain of roughly 72.8 million across the century. That is genuine growth, and it is rare: of the ten most populous countries today, four are still rising when the projection window closes, and among the three largest, the United States is the only one in that position.

The growth is also thinning fast. The annual growth rate was about 1.47% in 1950 and 0.99% in 2000; it is roughly 0.49% now, falls to about 0.23% by 2050 and reaches 0.13% by 2100. The country passed 200 million in 1968, crosses 350 million around 2028, and does not reach 400 million until about 2073. Each subsequent hundred million takes far longer than the last.

It is not fertility

The intuitive explanation is that Americans have more babies. The data does not support it. The United States records about 1.62 births per woman in 2026, well under the roughly 2.1 needed for a generation to replace itself, and France records a higher rate. Five of the other six are below it, but not by the margin the reputation implies. The American position on that chart is ordinary, as the fertility line most of the world is now below sets out at length.

Sub-replacement fertility has a mechanical consequence, and the projection has the United States meeting it on schedule. From about 2042, American deaths outnumber American births every year to the end of the century. Summed from 2026 to 2100, natural change comes to roughly 22.5 million fewer people. On births and deaths alone, the United States shrinks.

Migration is doing all of the work

Over the same period the projection adds about 95.8 million through net migration. That is more than the total growth, because it first has to cover the deficit from births and deaths and only what is left over shows up as an increase. Put plainly: every net addition to the American population in the second half of this century arrives, or is descended from someone who did.

The scale is what makes the United States unusual rather than the direction. Across every country with a net inflow between now and 2100, the United States absorbs about 36% of the world total, with Russia a distant second at roughly 22.9 million. This is the single assumption the whole American projection rests on, and it is the least predictable of the three components that drive a projection, because it is set by policy rather than by biology.

Which peers actually shrink

The premise deserves a check. Of the six other G7 countries, three have already passed their maximum population: Japan (2010), Germany (2024) and Italy (2014). The remaining three have not: United Kingdom (peak dated 2073), France (peak dated 2096) and Canada (peak dated 2100). So the United States is not alone, and the honest version of the headline is narrower than the usual one.

What divides the two halves is not fertility. Of the four members still growing, the lowest birth rate belongs to Canada at about 1.33, below the American figure and below Germany, which has stopped growing. Canada sustains an average net inflow of about 5.7 migrants per thousand residents a year from here to 2100, against 3.3 for the United States.

The clean test is not the size of the inflow but whether it covers the birth deficit. Dividing cumulative net migration by the cumulative shortfall of births against deaths, every G7 country still growing comes out above 1 and every one already past its peak comes out below it. Germany takes in more migrants over the period than France does and still shrinks, because its birth deficit is several times larger. The United States comes out at about 4.3 times its own deficit, the widest cushion in the group. The dividing line inside the rich world is whether immigration outruns the birth deficit, not family size, a pattern visible across the continent in Europe’s quiet population decline and in our ranking of countries past their peak.

Growing, and still slipping down the table

Growth does not protect a ranking. The United States is 3rd in the world today and 6th in 2100, passed by Pakistan, Nigeria and DR Congo despite adding tens of millions of people itself. Being overtaken while growing is the ordinary experience of this century for a mature economy. Nigeria passes the United States around 2057, at roughly 386 million people each, and the full order sits in our largest countries in 2100 ranking.

In share terms the picture is flatter than either story suggests. The United States held about 6.2% of world population in 1950 and about 4.2% today, and the projection has it near 4.1% in 2100. It keeps pace with a world that itself stops growing around 2084.

Aging anyway, just more slowly

Migration buys population, not youth, though it slows the ascent. The American median age is about 38.7 in 2026, rising to 41.9 by 2050 and 45.3 by 2100. That is 45th oldest among the 161 places above a million people today, which is to say unremarkable. Japan, Germany and Italy are already older today than the United States is projected to be in 2100. A country can grow and age at the same time, and this one does both.

How much of this is actually known

Less than the single line suggests. The central projection ends at 421 million, but the low fertility variant peaks around 2043 at roughly 355 million and then falls to about 308 million by 2100, while the high variant reaches 565 million. The variants disagree not merely on how much the United States grows but on whether it grows at all. Anyone quoting a single 2100 figure for the United States is quoting the middle of a very wide band.

Two further cautions. A peak dated to 2100 does not mean a country grows forever; it means the projection window closes before the series turns, and on present fertility the turn is waiting on the far side of it. And the migration assumption that drives the whole result is a projection of policy, which can change in a single legislative session in a way that fertility and mortality cannot.

All figures here come from the UN World Population Prospects 2024 medium variant unless a variant is named, processed as described in our methodology, with population read on 1 January of each year and births, deaths and net migration read for the calendar year. Cumulative totals are sums over the annual series from 2026 to 2100 inclusive.