What methods do US agencies use to estimate total illegal entries and encounters under Biden?
Executive summary
U.S. agencies primarily rely on operational “encounters” recorded by U.S. Customs and Border Protection (CBP), supplemented by component tallies for apprehensions, inadmissibles at ports, expulsions, and technology-detected “got‑aways”; outside analysts and political actors then adjust those raw counts with modeling and assumptions to produce higher estimates of total illegal entries or net population change [1] [2] [3]. Those methods are transparent in places but fragmented, produce different denominators (encounters vs unique individuals vs net new residents), and are routinely misread or amplified in partisan reporting [4] [5].
1. The core operational metric: “encounters” recorded by CBP
CBP’s headline figure is the number of “encounters,” a raw tally that aggregates Border Patrol Title 8 apprehensions, Office of Field Operations inadmissibles at ports of entry, and Title 42 expulsions, and is published as nationwide and regional time series that reporters and lawmakers use as the basic volume measure [1] [2]. Analysts and the public often treat encounters as a proxy for illegal entries, but CBP encounters count each person stopped (so repeat crossings or family groups are each counted) and mix different legal outcomes in a single series, a nuance emphasized by news outlets and fact‑checkers [2] [5].
2. Apprehensions, releases and expulsions: different outcomes in the same ledger
Within the encounter framework, agencies separately track people who are processed and removed or expelled, those deemed inadmissible at ports and paroled, and those released into the United States pending immigration proceedings; fact‑checking organizations note that totals of released versus removed vary by month and have driven many partisan percentage claims about “releases” [4] [5]. Congressional and executive branch actors cite partial slices of this data to support policy narratives, for instance contrasting CBP removals with claims about large numbers being “released,” a comparison that FactCheck and PBS have warned can conflate short windows and different encounter types [4] [5].
3. “Got‑aways” and technology: estimating undetected crossings
CBP and lawmakers also attempt to account for people who were detected by sensors, cameras or agents but never apprehended — the so‑called “got‑aways” — using Border Patrol testimony and technology logs to add an estimate of undetected or ultimately unprocessed crossings to the encounter count [3] [6]. Those technology‑based figures are imperfect and often reported as conservative minima (e.g., hundreds of thousands in some fiscal years according to Border Patrol testimony), and they are frequently invoked by critics to argue the official encounter numbers undercount true crossings [3].
4. Ports of entry, parole programs and shifting classifications
Changes in policy — such as expanded humanitarian parole programs that allow lawful entry at ports of entry — shift where and how migrants are recorded, with CBP data showing a larger share of nationwide encounters at ports in certain months and administrations, complicating comparisons over time [7] [2]. Political actors use those classification shifts to argue either that encounters overstate illegal crossings because more people are entering legally at ports, or that programs enable mass inflows; both interpretations lean on the same CBP encounter buckets but read different policy judgments into them [7] [2].
5. External modeling, net population estimates and partisan tallies
Because encounters do not equal unique new residents, outside groups and scholars apply demographic models, immigration survey data, and assumptions about re‑encounters, emigration, and overstays to estimate net unauthorized population change; examples include think‑tank and congressional staff calculations that extrapolate releases and “got‑aways” into multi‑year totals — methods that vary widely and produce partisan discrepancies [3] [2]. Independent journalists and fact‑checkers caution that headline claims using those extrapolations (e.g., “X million have come in illegally”) depend on assumptions — about repeat crossings and eventual removals — that are unresolved in public data [4].
6. Limitations, interpretation and political use of the methods
All methods — raw CBP encounters, technology‑informed “got‑away” estimates, and external demographic modeling — carry measurement limits: encounters can double‑count, technology detects but does not prove successful entry, parole or inadmissible classifications alter comparability, and models require untestable assumptions; fact‑checking outlets and CBP’s own documentation emphasize these constraints while political actors selectively amplify figures that support their narratives [1] [5] [4]. Public reporting therefore needs to keep the metrics distinct — encounters vs unique crossings vs net additions to the unauthorized population — and recognize that agencies provide building blocks, not a single definitive count, for the question of how many people enter unlawfully under any administration [1] [2].