Fact check: How many illegal aliens are in the united states

1. Summary of the results

The estimates for the number of unauthorized immigrants in the United States vary significantly depending on the source and methodology used. The most recent estimates range from 12.2 million to 18.6 million as of 2023-2025.

The Federation for American Immigration Reform (FAIR) provides the highest estimate at 18.6 million illegal aliens as of March 2025, representing an 11% increase from their June 2023 estimate of 16.8 million ^[1]. The Center for Immigration Studies estimates 15.4 million illegal immigrants in January 2025, noting a 5.4 million increase from January 2021 to January 2025 ^[2].

In contrast, Pew Research Center reports a more conservative estimate of 11.0 million unauthorized immigrants in 2022, marking the first increase since 2019 but not accounting for developments since mid-2022 ^{[3] [4]}. A separate academic source estimates the undocumented population reached 12.2 million in 2023, exceeding the previous 2008 high of 12.0 million, with a two million increase from 2020 to 2023 ^[5].

2. Missing context/alternative viewpoints

The original question lacks crucial context about the significant methodological differences between organizations that produce these estimates. Different organizations use varying definitions, data sources, and statistical models, which explains the wide range in estimates.

Political and organizational motivations significantly influence these numbers. FAIR, which advocates for immigration restriction, consistently produces the highest estimates and explicitly attributes growth to "the Biden administration's policies and the mass release of illegal aliens apprehended at the border" ^[1]. Organizations like FAIR and the Center for Immigration Studies benefit from higher estimates as they support their advocacy for stricter immigration policies and increased funding for enforcement.

Conversely, Pew Research Center, which positions itself as nonpartisan, provides more conservative estimates that may be preferred by organizations advocating for immigration reform or expanded pathways to legal status, as lower numbers can make the issue seem more manageable.

The analyses reveal important demographic shifts often missing from public discourse: Mexico now accounts for only 4 million unauthorized immigrants, the lowest since the 1990s ^[4], while there has been significant growth from Central America, South America, and Asia ^[5].

3. Potential misinformation/bias in the original statement

The original question uses the term "illegal aliens," which is politically charged language that reflects a particular ideological perspective. This terminology is primarily used by immigration restrictionist organizations like FAIR ^[1] and suggests a framing that may predispose readers toward viewing unauthorized immigration as inherently criminal rather than a civil matter.

The question's simplicity obscures the complexity of immigration status categories and fails to acknowledge that estimates vary dramatically based on methodology and political perspective. By not specifying a timeframe or acknowledging the range of estimates, the question implicitly suggests there is a single, definitive answer when the reality is far more nuanced.

The framing also omits important context about historical trends - that unauthorized immigration had been declining for over a decade before recent increases ^[3] - and demographic changes in the composition of this population that are crucial for understanding current immigration patterns.