The immigration surge of the past few years has been the largest in U.S. history, surpassing the great immigration boom of the late 1800s and early 1900s, according to a New York Times analysis of government data.

Annual net migration — the number of people coming to the country minus the number leaving — averaged 2.4 million people from 2021 to 2023, according to the Congressional Budget Office. Total net migration during the Biden administration is likely to exceed 8 million people.

That’s a faster pace of arrivals than during any other period on record, including the peak years of Ellis Island traffic, when millions of Europeans came to the United States. Even after taking into account today’s larger U.S. population, the recent surge is the most rapid since at least 1850.

The numbers in the Times analysis include both legal and illegal immigration. About 60% of immigrants who have entered the country since 2021 have done so without legal authorization, according to a Goldman Sachs report based on government data.

The combined increases of legal and illegal immigration have caused the share of the U.S. population born in another country to reach a new high, 15.2% in 2023, up from 13.6% in 2020. The previous high was 14.8%, in 1890.

Causes and effects

Several factors caused the surge, starting with President Joe Biden’s welcoming immigration policy during his first three years in office. Offended by Donald Trump’s harsh policies — including the separation of families at the border — Biden and other Democrats promised a different approach. “We’re a nation that says, ‘If you want to flee, and you’re fleeing oppression, you should come,’” Biden said during his 2020 presidential campaign.

After taking office, his administration loosened the rules on asylum and other immigration policies, making it easier for people to enter the United States. Some have received temporary legal status while their cases wend through backlogged immigration courts. Others have remained without legal permission.

Outside causes have also played an important role in the surge. Turmoil in Haiti, Ukraine and Venezuela caused desperate people to flee their home countries. The growth of smuggler networks run by Mexican drug cartels allowed more people to reach the U.S. border. But the Biden administration’s policy appears to have been the biggest factor: After Biden tightened enforcement in June, the number of people crossing the border plummeted.

The scale of recent immigration helps explain why the issue has played a central role in American politics over the past few years.

Mayors and governors, both Democratic and Republican, have complained about the strain on local government. In Chicago and elsewhere, residents have filled public meetings to make similar criticisms. In Denver, where tens of thousands of migrants have arrived, homeless people say that shelter spots are harder to find. In the Queens borough of New York City, residents say that an influx of street vendors has created chaos in some neighborhoods.

Some of the biggest effects have occurred in South Texas, and Trump made big electoral gains there. Eight years ago, he won less than 30% of the vote in a strip of six counties along the Rio Grande. This year, he won all six counties.

Elsewhere, Democrats who managed to outpace Vice President Kamala Harris and win tough congressional races — including in Arizona, Maine, Michigan, Nevada, New York and Wisconsin — frequently criticized Biden’s border policies. Polls suggest that the immigration surge was Harris’ second-biggest vulnerability, after only the economy.

Voters expressed particular frustration with the high recent levels of illegal immigration. Of the roughly 8 million net new migrants who entered the U.S. during the Biden presidency, about 5 million did so without legal authorization, according to Goldman Sachs.

Some Republican politicians, including Trump, have spread falsehoods about recent immigrants, claiming that they have caused a crime wave. In truth, immigrants have historically committed crime at lower rates than native-born Americans, and crime fell nationwide over the past few years as immigration levels spiked.

Similarly, academic research suggests that the immigrants of recent decades, who have come primarily from Asia and Latin America, are climbing the economic ladder and assimilating into American society. Their children and grandchildren have made progress at a pace similar to that of the predominantly European immigrants of the late 1800s and early 1900s.

But high levels of immigration do have downsides, including the pressure on social services and increased competition for jobs. The Congressional Budget Office has concluded that wage growth for Americans who did not attend college will be lower than it otherwise would have been for the next few years because of the recent surge. On the flip side, higher immigration can reduce the cost of services and help Americans, many with higher incomes, who do not compete for jobs with immigrants

Bernard Yaros Jr., a lead U.S. economist at Oxford Economics, a research firm, described the recent increases as “something that we really haven’t seen in recent memory.” Yaros said that they had “helped cool wage growth.”

Census Undercount

Even with all the political attention on immigration, the precise size of the surge has been unclear because of the different ways that the federal government collects data. When looking at the distant past, researchers rely on once-a-decade Census Bureau surveys of the population. Those surveys include a question about birthplace.

But over the short term — and especially during periods of change — the Census Bureau can underestimate the size of the immigrant population, outside researchers say. For one thing, some immigrants, especially those without legal status, are likely to avoid replying to surveys. And the census uses a statistical technique that assumes that the country’s population is not changing rapidly from year to year, rather than trying to measure precisely how it might have grown.

Julia Gelatt, associate director of the U.S. Immigration Policy Program at the Migration Policy Institute in Washington, noted that the census also undercounted the immigration population in the 1990s, when levels were rising. It later revised those numbers upward.

For these reasons, researchers have more faith in recent data collected by the Congressional Budget Office. It combines surveys with administrative data on border crossings, asylum applications and other immigration records to estimate net migration.

Private firms that have conducted their own analyses of government data — such as Goldman Sachs and Oxford Economics — have come to similar conclusions as the CBO. Officials at the Federal Reserve use the CBO’s estimates rather than Census Bureau’s when making decisions about monetary policy. Jerome Powell, the Fed chair, recently said that the actual levels of recent immigration were “likely not fully reflected” in the census numbers. A study by the Boston Fed described its conclusions as “consistent with the CBO’s findings of very large increases in immigration.”

An annual census survey, known as the American Community Survey, shows net migration of only 900,000 from 2020 to 2023. The CBO, Goldman Sachs and Oxford Economics all estimate that net migration exceeded 2 million people during those years and likely will again this year.

The Future

What happens next is less clear. During the presidential campaign, Trump promised to conduct mass deportations, and many Americans favor the policy. In a New York Times/Siena College poll conducted in October, 57% of voters said they supported deporting immigrants who were living in the country illegally.

But the logistics of finding, apprehending and deporting millions of people would not be simple. Public support for the policy could decline if it swept up immigrants who had been in the country for years and established lives here. As a point of comparison, the Trump administration deported about 300,000 people per year, and the Obama administration deported almost 400,000 per year.

Whatever the number in a second Trump term, the recent immigration surge has probably ended. Biden’s crackdown since the summer has caused net migration to drop sharply, and Trump has promised even tougher border policies when he takes office. Many would-be immigrants will be less likely to try to enter the country, knowing that their chances of success are lower.

There is an historical echo with a century ago. The immigration wave of the late 1800s and early 1900s also sparked a political backlash, leading to a 1924 law that tightly restricted immigration. Those restrictions remained largely in place for more than four decades.

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More on the data: The Times analysis of recent immigration relied on census data until 2019 and a combination of census and CBO data since 2020. We worked with experts in the government and elsewhere to pair the two data sets.

The census data is based on surveys. The CBO data is based on both surveys and administrative records from immigration courts, border officials and other government agencies. Data from 1850 to 2000 comes from the decennial census; from 2010 to 2019, data comes from the American Community Survey; and from 2020 to 2023, it comes from the ACS and the CBO.

Outside experts, including those at the Federal Reserve, consider the CBO’s recent estimates to be more accurate. Some experts do think the CBO estimate — of 2.4 million per year from 2021 to 2023 — is too high because it relies on administrative data that may miss some immigrants who return to their home countries. Other estimates are somewhat lower than those from the CBO. Goldman Sachs, for example, estimates annual net migration as just above 2 million per year from 2021 to 2023.

But the recent immigration surge has been so large that the central conclusions of our analysis remain even if the Goldman Sachs estimate is more accurate than the CBO estimate: The recent immigration surge is the largest in U.S. history, and the foreign-born population has reached a new high.

In another way, our analysis understates the immigration surge because the analysis ends in July 2023. (The census’ main population estimates are for July 1 of the listed year.) Immigration remained high for about 12 months after the summer of 2023, until Biden’s crackdown.

In July of this year, the foreign-born share of the U.S. population reached 15.5%, the Goldman Sachs numbers suggest. CBO’s estimates suggest the share was about 16%. In 2020, the share was 13.6%. The previous high of 14.8% occurred in 1890.

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This article originally appeared in The New York Times.

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