With the 2024 presidential election nearly upon us, the issue of immigration has become a prime subject of discussion – and more accurately, division. Vitriolic anti-immigrant rhetoric has become so commonplace that we’ve lost the edge of outrage toward nativism that would have been the public’s response just a few years ago.

Perhaps the biggest loss to the national conversation is a realistic assessment of the role immigration plays in sustaining the economy’s vitality. But the handwriting on the wall is pretty clear: Unless we allow immigrants to fill the workforce gaps left by a combination of rapid population aging and low birth rates, there is little hope of sustaining growth in living standards for those already here.

Need some convincing? Start with the latest projections released by the U.S. Census Bureau. They show what would happen to population in the decades ahead in a variety of scenarios – that is, if immigration were higher, lower, stayed the same or were driven down to zero.

Moderate immigration rates (850,000-980,000 annually), which would be roughly the same as the flows seen in recent decades, would be sufficient to sustain some population growth through 2080 before tapering off. Low immigration (350,000-610,000), experienced during the later years of the Trump administration, would yield a population peak in 2043 but would end the century below current levels. A high immigration scenario (1.45-1.60 million), by contrast, would lead to continued population growth over the rest of the century, ending with 100 million more residents than today.

The “zero immigration” scenario – no new in-migrants along with an expected trickle of out-migrants – is perhaps the most interesting in light of the current political climate. Total population would begin to decline in the next decade, and by the end of the century would fall by 100 million.

Note that even if the moderate immigration scenario holds over the next decade, the overall rate of growth of the population would still be slower than in any past decade in history. Specifically, growth in the next two decades would be just 4.1 percent and 3 percent, respectively – and thereafter no higher than 1.5 percent per decade. For purposes of comparison, the decade of the 1950s saw population growth of more than 18 percent.

One reason all of this matters is that immigration affects aging and economic dependency. Under all immigration scenarios – high, low, zero – aging is baked in because, going forward, proportionately few women will be of childbearing age. Likewise, the youth (under age-18) population will decline under all immigration scenarios. But immigration still makes a big difference: Because immigrants and their children are younger on average than the resident U.S. population, the higher the pace of immigration the lower the pace of aging.

From the perspective of economics, this is most consequential for the size of the future working population, particularly over the next decade, during which the last reverberations of the baby boom will add years to the average age of the native population. In almost any scenario, the ratio of workers to oldsters dependent on Social Security, Medicare and Medicaid will fall, forcing Washington to choose between allowing workers to keep the fruits of their productivity growth and delivering on promises to the aging. Over the long term, dependency will rise less sharply. But without substantial immigration, the strains on social entitlement programs will remain daunting.

Americans want the America they grew up in, proclaim advocates of the Great Replacement Theory. Immigration-as-usual, they lament, means an ever-less-white America. They’re right: under any immigration scenario – not just a high immigration scenario – America’s population will become more racially (and ethnically) diverse.

Projecting through the year 2060, the portion of the population that is white will certainly decline because, on average, the age of white Americans today is substantially higher than that of non-white Americans. Indeed, the U.S. Census Bureau concluded that all net gains to the United States population going forward will be attributable to non-white groups.

Of these groups, the Hispanic population is likely to show the largest gains under each of the immigration scenarios. While Hispanic people are projected to make up sizeable portions of future immigration flows, their large share of the U.S. population today (19 percent) and relatively young average age ensures that their natural increase would loom large even under the low- or zero-immigration scenarios.

By 2029, the under-age-35 population will be “minority white” under all immigration scenarios. By 2040, the white population will comprise no more than 55 percent of the total population. And by 2050 white people will be a minority of the population under the high, moderate and low immigration scenarios.

We are at the cusp of making important decisions about immigration. At first glance, allowing the population to decline as death rates exceed birth rates among the native population might not seem like such a bad thing.

Think reduced pressure on the environment, easing of traffic and local housing shortages, slowing the deterioration of aging infrastructure. Indeed, back in the 1960s and 1970s a lot of sensible people thought zero (or negative) population growth was essential if the United States (and the rest of the world) were to avoid a grim Malthusian future.

But a second glance suggests the price of allowing this to happen quickly – that is, within decades – would be high. Other things equal, one could imagine the virtues of a world in which half as many people competed for the natural resources of the planet. But other things are not equal. Stopping or reversing population growth by putting the brakes on U.S. immigration would reduce the portion of the population of working age, which would act as a ruinous drag on average productivity.

Put more plainly, if immigrants are denied entry, who will be there to take care of the growing ranks of older Americans? Equally to the point, though less talked about, who will sustain America’s pace of innovation if the best and brightest can no longer come to America to take advantage of its vaunted system of higher education, entrepreneurial flexibility and efficient capital markets?

For most of U.S. history, immigrants have fed America’s voracious demand for labor, with almost everyone benefitting as a consequence. Just how much we’d lose if we shut the door now is not fully known. Perhaps robots could keep our nursing homes going. Perhaps AI could sustain productivity growth in a world of scarce labor. But I, for one, would prefer not to find out.