FIRST ON FOX: The number of illegal immigrants in the U.S. is estimated to have surged to more than 18 million after the Biden-era border crisis, according to a new research report by a hawkish immigration group, which also found an 11% increase in less than two years.
The report was produced by the Federation for American Immigration Reform (FAIR), which argues for lower levels of immigration overall. It estimates that, as of March 2025, there are approximately 18.6 million illegal immigrants living in the U.S.
That is 11% higher than an estimate the group published in June 2023, when it found that there were 16.8 million illegal immigrants. Overall, it estimates that the population has grown by 4.1 million or 28.2% since December 2020.
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“As of 2025, American population growth comes almost entirely from unsustainably high levels of immigration, both legal and illegal,” the report says.
President Donald Trump addresses a joint session of Congress at the U.S. Capitol on March 4, 2025 in Washington, D.C. (Win McNamee/Getty Images)
FAIR estimates that there were around 11.7 million illegal immigrants in 2013.
The group includes, as an illegal immigrant, anyone who does not have legal status like a visa or permanent residency, and notably also includes those who may be in the country illegally but given a lawful presence, like Temporary Protected Status or humanitarian parole.
The Biden administration dramatically expanded the use of humanitarian parole as a way to curb skyrocketing illegal border crossings. It allowed migrants to cross the border after scheduling an appointment on the CBP One app for parole, and had parole programs where migrants could fly in having obtained travel authorization.
FAIR argues that even though they are described as having a “lawful presence,” they do not have legal status and therefore cannot be counted as being in the country legally.
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“Counting individuals in these situations as ‘legal immigrants’ or ‘lawful residents’ would be both incorrect and a biased mischaracterization of immigration law,” the group argues.
Former Homeland Security Secretary Alejandro Mayorkas led the department during the 2021-2024 border crisis. (Getty Images)
The report estimates the total number of illegal immigrants by using Census Data and compensating for what it argues is a history of undercounting those who arrive illegally, calculating an undercount of around 40%.
The report also concedes that “estimating the size, distribution, and characteristics of the illegal alien population is an inexact science.”
“In truth, we do not know exactly how many people cross the border illegally and evade immigration authorities, nor can anyone accurately quantify overstays or gotaways. We can only estimate these figures based on annual and monthly census data,” the report says.
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It argues that key factors driving the surge in numbers were Biden-era policies, including at the border, the release of migrants into the U.S. and what it claims was an “abuse” of parole authority.
The Trump administration, which took office in January, has reversed a number of Biden policies and has shut down the parole policies and the use of the CBP One app. It has also launched a mass deportation campaign in the interior, while also deploying the military to the border and declaring a national emergency.
The administration has since been touting a sharp drop in numbers at the border.
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In February, there were just 8,326 southern border encounters, down from 189,913 in February 2024. The administration has so far removed more than 55,000 illegal immigrants from the U.S.
“Within hours of taking the oath of office, I declared a national emergency on our southern border and I deployed the U.S. military and Border Patrol to repel the invasion of our country. And what a job they’ve done. As a result, illegal border crossings last month were by far the lowest ever recorded, ever,” President Donald Trump said on Tuesday.
“They heard my words, and they chose not to come.”
