Fact check: What is the estimated number of illegal aliens living in the US as of 2025?

1. Summary of the results

Based on the analyses provided, estimates for the number of undocumented immigrants in the US as of 2025 vary significantly depending on the source and methodology used:

Most Recent Estimates:

• The Center for Immigration Studies (CIS) provides the most specific 2025 estimates: 14.8 million as of May 2025 ^[1] and 15.8 million as of January 2025 ^[2]
• These CIS estimates suggest a decrease from January to May 2025, with the population dropping from 15.8 million to 14.8 million ^[1]

Range of Estimates:

• Conservative estimates: Around 11 million (Biden administration estimate) ^[3]
• Higher estimates: Up to 18-20 million from conservative and anti-immigration groups ^[3]
• CIS methodology: Estimates 15.4 million in the January 2025 Current Population Survey, representing 29% of the total foreign-born population ^[2]

Border Enforcement Impact:

• Significant policy changes are reflected in border data: 0 illegal aliens released by U.S. Border Patrol in May 2025, compared to over 62,000 releases in May 2024 ^[4]

2. Missing context/alternative viewpoints

Methodological Limitations:

The analyses reveal important caveats that affect accuracy. The CIS estimates acknowledge that immigrants may be reluctant to respond to surveys or identify as foreign-born due to stepped-up enforcement efforts ^[1]. This suggests the actual numbers could be higher than survey-based estimates indicate.

Political and Economic Interests:

Different stakeholders benefit from promoting different estimates:

• Anti-immigration organizations and conservative groups benefit from higher estimates (18-20 million range) as this supports arguments for stricter enforcement and larger deportation operations ^[3]
• The Biden administration and pro-immigration advocates benefit from lower estimates (around 11 million) as this minimizes the perceived scope of undocumented immigration ^[3]
• The Center for Immigration Studies, which produced the most detailed 2025 estimates, is known for advocating immigration restrictions, which could influence their methodology and presentation

Historical Context:

The analyses show a 5.4 million increase since January 2021 ^[2], providing important context about recent immigration trends that directly relates to policy changes between administrations.

Census Implications:

President Trump's announcement to exclude undocumented immigrants from census counts ^[5] adds political significance to these population estimates, as they could affect congressional representation and federal funding distribution.

3. Potential misinformation/bias in the original statement

The original question uses the term "illegal aliens," which is politically charged language. While not technically incorrect, this terminology reflects a particular ideological framing that emphasizes the legal status violation rather than using more neutral terms like "undocumented immigrants."

Precision vs. Reality:

The question asks for "the estimated number" as if there were a single, authoritative figure. However, the analyses demonstrate that estimates vary dramatically from 11 million to 20 million ^[3], and methodological challenges make precise counting extremely difficult.

Survey Limitations:

The most detailed estimates come from Current Population Survey data ^{[2] [1]}, but these surveys may significantly undercount undocumented populations due to fear of enforcement and reluctance to participate in government surveys ^[1]. This systematic undercounting bias means that survey-based estimates likely represent minimum rather than actual numbers.

Source Concentration:

Most of the specific 2025 estimates come from a single organization (CIS) ^{[2] [1]}, which limits the diversity of methodological approaches and could introduce systematic bias into the available estimates.