The US prides itself on being a "nation of immigrants," but immigrants actually make up a smaller share of the population in America than they do in Australia, Spain, or many other countries. In fact, when it comes to immigration per capita, the US is still below where it was in 1890.
A new Census Bureau projection estimates that in the 21st century, the US will finally surpass the record it hit in the 19th century. In 1890, 14.8 percent of people living in the US were born in another country. The Census Bureau anticipates that the US will hit that point again as soon as 2025 — and that by 2060, as much as 18.8 percent of the US population will be foreign-born:
The prediction isn't because the Census thinks immigration to the US is going to spike. The Census Bureau assumes immigration will increase gradually, which is in line with what current US policies allow. (Any radical change would require Congress to change legal immigration policy, and the Census Bureau isn't making any assumptions about whether or when that will happen.)
Instead, it's because the US birth rate, which remained at an all-time low in 2013, is projected to continue to decline across all ethnic groups. For native-born Americans, there will still be more births than deaths each year. But they'll be having fewer children in 2060 than they are now.
In other words, there will be more immigrants coming into the US in 2020 than there are right now. But there will be fewer babies born in the US in 2020 than there are right now. Both of those trends are going to continue. As a result, the number of immigrants will grow faster than the number of native-born Americans — so the share of people living in America who are immigrants will increase.
This is already happening in parts of the country, like the Great Plains:
The Census anticipates that this is going to play out very differently among different races. Non-Hispanic whites, for example, are actually going to hit negative "natural growth" by 2020 — more non-Hispanic whites will die that year than be born. So even though the Census Bureau doesn't think non-Hispanic whites are going to start migrating to the US in tremendous numbers, it still anticipates that the foreign-born share of the white population is going to grow. (The foreign-born share of the black population will also grow, but that's partly because the Census believes that more black immigrants are going to come as time passes.)
But among the two largest immigrant groups to the US — Hispanics and Asians — the opposite is going to happen.
Hispanic and Asian immigrants will keep coming in, but at roughly the same pace they are today: the Census projects that the number of Hispanic immigrants will increase from 535,000 in 2015 to 550,000 in 2060, while the number of Asian immigrants will increase from 355,000 to 404,000 over that same time period. Meanwhile, the Hispanics and Asians that are already here will continue to have children — and new Hispanic and Asian immigrants will continue to have children after they arrive. The Hispanic birthrate, in particular, is the highest in the US for any single race, and the Census projects that will continue. So the foreign-born shares of the Hispanic and Asian American populations will actually decrease over the next half century.
Any projection about ethnicity in the future should be taken with a big grain of salt. We have no way of knowing for sure who'll even be considered "white" in 2060. The Census projects that the fastest-growing share of the population, by far, is going to be Americans of "two or more races," which has the potential to totally scramble racial categories as they exist today.
Furthermore, just because people consider themselves nonwhite now doesn't mean their children or grandchildren will identify the same way. This is an especially big question for Latinos right now, with some evidence that some grandchildren of Latino immigrants are more likely than others to consider themselves white — and even evidence that some people go from considering themselves Latino when they respond to one Census to considering themselves white when they respond to the next Census 10 years later.
Because of all this, the Census estimates aren't as reliable for individual ethnic groups as they are for the entire US population; projecting how many people will be born, die, or immigrate is easier than predicting how they'll identify themselves. That said, a massive change to immigration policy — if some hypothetical future Congress decided to pass comprehensive immigration reform, for example — would throw a wrench into the Census' projections. After all, more restrictive immigration policies are the reason that the immigrant share of the US population declined through the first two-thirds of the 20th century; then, the Immigration Act of 1965 reversed that decline and is the reason for the growing — and more diverse — immigrant population today.