“Our Country,” President Donald Trump says, “is FULL!”

America is the 146th most densely populated country on earth, sandwiched between Venezuela and Kyrgyzstan. Still, immigration is about more than land. People who say America is full are arguing that the costs immigrants impose outweigh the benefits. Those costs can be cultural, economic, or even political.

I’m the son of an immigrant, and I grew up in Orange County, California, a particularly immigrant-heavy enclave in an immigrant-heavy state. When I return home, even now, Orange County’s health is obvious. The unemployment rate is 2.6 percent, startups fill office parks, new construction dots the roadways. Growth can carry its own challenges — housing prices have skyrocketed, traffic on the 405 is a nightmare — but it beats contraction.

Yet through our suspicion of immigration, much of America is choosing contraction.

Here’s a fact that should get a lot more attention than it does: America is growing more slowly than at any time since the Great Depression. The culprits here are many: The population is aging, birthrates are falling, and immigration is flat. But altogether, America is adding 900,000 fewer people each year than was our 20th-century norm, with 2018 showing the slowest rate of growth in more than 80 years.

But it’s the geography of America’s Great Growth Slowdown that’s really worrying. A new report from the Economic Innovation Group shows that America’s population growth is increasingly concentrated in an ever-smaller number of counties, while the declines are spread across ever more counties. So though America’s population is growing overall, half of US counties are shrinking each year, and “over 50 million people, or 15% of the U.S. population, live in counties that have shrunk over the past decade.”

The story is even scarier if you’re looking at adults in the prime working years of 25 to 54 — a particularly important group for driving economic growth and tax revenues. Fully 80 percent of counties have seen population losses among prime working-age adults over the past decade. The authors note that if current trends continue, “67% of U.S. counties will contain fewer prime working age adults than they did in 1997.”

As you’d expect, low-growth places struggle across a host of economic measures. If you compare employment rates between the fastest-growing and fastest-shrinking counties, “the 12 percentage point gap between these two groups of counties is significantly larger than the 7 percentage point increase in non-employment the United States experienced during the Great Recession.”

These communities also see weaker housing markets, higher borrowing costs, and more vacant properties. And because these communities were larger in the past, they find themselves struggling to support infrastructure built for a bigger tax base than they now have.

All of this can create a cycle of exit, in which the residents most able to find jobs elsewhere flee, leaving the economy even weaker, which drives out the next tranche of residents with the best opportunities elsewhere, and so on.

America’s political system is structured to advantage sparsely populated areas over densely populated ones. To the extent that more areas are seeing populations stagnate and even decline, and more economic growth is concentrated in the fastest-growing zip codes, turbulence is to be expected. Arguably, it’s already here.

“The less-than-500 counties that Hillary Clinton carried nationwide encompassed a massive 64 percent of America’s economic activity as measured by total output in 2015,” Mark Muro and Sifan Liu found in their analysis of the 2016 election results. “By contrast, the more-than-2,600 counties that Donald Trump won generated just 36 percent of the country’s output — just a little more than one-third of the nation’s economic activity.” That’s a sharp jump from 2000, when Al Gore’s 659 counties accounted for 54 percent of GDP.

For both economic and political reasons, we should worry about the consequences of depopulation. And the most powerful tool we have to address them is immigration.

More people, fewer problems

Skilled immigrants are good for economies. They start businesses at high rates, raise housing prices, generate new demand, and contribute far more in state and local taxes than they remove (about $105,000 more, according to the National Academy of Sciences).

But right now, skilled immigration adds to geographic inequality rather than easing it. The 20 most populous US counties have 37 percent of the skilled immigrants but only 19 percent of the population. “Thus,” the EIG authors write, “the flow of human capital from abroad is one more way in which struggling, shrinking parts of the country are falling further behind.”

It’s worth noting that our intuitions about the effect of skilled immigrants are often really, really wrong. People tend to imagine the supply of jobs as fixed, and immigrants as competing for them with native-born workers. And what do you get when you have more people competing for the same jobs? Lower wages.

But the supply of jobs is not fixed, and more skilled, entrepreneurial workers create more jobs — that’s why education is good for economies, and why workers with in-demand skills flock to the places with the most other workers with in-demand skills. The wages of computer programmers in San Francisco aren’t high in spite of all the other computer programmers; they’re high because of all the other computer programmers.

It’s not just the mega-cities like San Francisco and Los Angeles that show this effect. The only reason that Mayor Pete Buttigieg is able to run for president is that South Bend, Indiana, has been a success story under his leadership. But that success has revolved around South Bend being open to immigrants: 60 percent of the area’s population growth in recent years has come from immigrants, and those immigrants have been more likely to hold a bachelor’s degree than the native population. As a result, South Bend’s population has grown, its unemployment rate has fallen faster than the rest of the state, its downtown has revitalized, and its housing market has recovered.

The EIG’s recommendation is to use immigration to revitalize shrinking communities and calm geographic inequality. The group wants to build a new skills-oriented, place-based visa system on top of the existing immigration system. You could imagine structuring a policy like this in a lot of ways, but the basic idea here is that states or regions should be able to “opt in” to get these visas — so these would be decisions made at the state or local level — which would allow skilled immigrants to move to the US so long as they agreed to work and settle in the area their visa came from for some period of time. Canada and Australia both have programs like this, and they work quite well.

To those of us who believe in immigration, both as a contribution to America’s soul and spirit and as a policy tool for managing some of our toughest challenges, the conversation over it can be maddening. Conservatives — Trump included — like to talk about running America as a business, but if there was a business that had the ability to attract the world’s best talent, on the terms it chose, at no real cost to itself, don’t you think that’d be a major part of its strategy? Don’t you think its leaders would be thrilled by their good fortune and obsessed with maximizing it?

Progressives, meanwhile, defend the rights of immigrants who are already here but are less comfortable speaking about immigration itself. For all the ambition that exists around single-payer health care and 70 percent marginal tax rates and Green New Deals, there’s no corresponding effort to change the terms of the national discourse around immigration. Even Julián Castro, the 2020 Democratic contender who’s been most outspoken on immigration, has structured his plan around easing enforcement rather than increasing legal immigration.

Much of the immigration debate is about values. It’s about the kind of country you want America to be, the kind of people you’re comfortable seeing in it. Those feelings run deep, and they’re rarely changeable through political argument. But sometimes the debate is, or pretends to be, about more tangible questions. No matter what Trump says, America isn’t full. In fact, the problem facing many, many communities is that they’re emptying, with devastating consequences for the residents left behind.

Immigration is the most powerful tool we have to help those communities. The question is whether we want to use it.

Further reading:

• The Economic Innovation group’s full report on Heartland Visas is worth a read. Even if you don’t agree with the policy idea, the discussion of how and where America is losing population is uncommonly lucid.

• “Immigration to the United States has not, historically, been an act of kindness toward strangers,” writes my colleague Matt Yglesias. “It’s been a strategy for national growth and national greatness.” Read the whole thing.

• For the other side of this debate, read David Frum’s Atlantic essay asking how much immigration is too much, and if you want to go very deep on the way immigration can trigger ethnonationalist backlash, Eric Kaufmann’s book Whiteshift is the place to start.