Fact Check: Assessing Claims of 20 Million Undocumented Immigrants Entering Under Biden Administration

Immigration figures have become a focal point of heated political debate as the Trump administration signals intentions to review immigration cases from the Biden years. Senior Trump adviser Stephen Miller recently claimed on Fox News that the administration would “accelerate efforts to review every single person added to this country over the last four years, all 20 million.”

This 20-million figure has gained traction in conservative circles but faces scrutiny from immigration experts and researchers who question its accuracy and the methodology behind such estimates.

According to the nonpartisan Pew Research Center, the undocumented immigrant population in the United States reached approximately 14 million in 2023—the highest level on record. This represents an increase from earlier estimates of around 11 million, but falls significantly short of the 20 million figure cited by Miller and other Republican officials.

Data from Pew also indicates that undocumented immigration had actually begun declining during Donald Trump’s first presidency as his administration implemented stricter border policies. The subsequent rise during the Biden administration represents a reversal of this trend, though not to the extent claimed by Trump allies.

Alex Nowrasteh, Senior Vice President for Policy at the libertarian Cato Institute, addressed these claims directly: “Vice President JD Vance and a collection of online conservative commentators have argued that, as president, Joe Biden let in 20 or 30 million illegal immigrants, swelling their population to 30-50 million. These numbers are an exaggeration, but there was a large increase in the illegal immigrant population during the Biden administration.”

Immigration statistics can be particularly confusing because of terminology. U.S. Customs and Border Protection uses “encounters” to record instances when an individual is stopped or apprehended attempting to cross the border unauthorized. An encounter does not necessarily mean successful entry into the United States, merely that authorities made contact with a person at or near the border.

These encounters can lead to various outcomes—immediate expulsion, deportation, or processing that may or may not result in a long-term stay. The numbers also count repeat crossers multiple times, potentially inflating the overall figure.

The Department of Homeland Security reported that more than 2 million undocumented migrants left the United States during the relevant period, including approximately 1.6 million who voluntarily self-deported and over 527,000 who were formally removed, according to an October 2025 press release.

Immigration patterns have shown fluctuations within the Biden term. In January 2025, the total immigrant population (both legal and undocumented) stood at 53.3 million, representing 15.8 percent of the U.S. population. By June of that year, departures and deportations had outpaced new arrivals, reducing the immigrant population to 51.9 million, or 15.4 percent of all U.S. residents.

The discrepancy between politically charged claims and research-based figures highlights the challenges of accurately quantifying immigration. Border enforcement metrics like “encounters” are often misinterpreted in public discourse, leading to inflated perceptions of the actual number of immigrants establishing residence in the country.

Immigration policy has become one of the most divisive issues in American politics, with Republicans generally advocating for tighter restrictions and Democrats supporting more flexible approaches. The Trump administration’s announced review of immigration cases from the Biden years signals that immigration will remain a central focus of the current presidency.

For context, border security and immigration policy have long been challenging issues spanning multiple administrations. The Biden administration faced criticism for record-high border encounters, while advocates noted that many factors—including regional instability, climate change, and economic disparities—drive migration patterns beyond any single administration’s policies.

What remains clear amid the political rhetoric is that the 20 million figure cited by Miller and others is not supported by data from nonpartisan research organizations that track immigration trends.