Home / Defense and security / Articles / What can the data tell us about unauthorized immigration?

Nearly 10 million migrants attempted to enter the US between October 2019 and January 2024, with record-high border apprehensions in 2022. Data on these border encounters —which include people denied entry into the country or apprehended trying to cross the border without inspection — helps the government estimate the number of individuals illegally entering the US.

By understanding the demographics and origins of people encountered at the border, policymakers can better understand the complex factors driving immigration and make informed policy decisions.

What is a border encounter?

The Department of Homeland Security separates border encounters into three categories:

  • Apprehensions are people temporarily detained by the US Border Patrol (USBP) for crossing the border illegally between ports of entry. They may or may not be arrested under Title 8 and can file for asylee status.
  • Inadmissibles are people seeking legal admission at official ports of entry who are found ineligible by officers of the Office of Field Operations (OFO) under Title 8. This category also includes people seeking humanitarian protection and people who voluntarily withdraw their admission application; they can also file for asylee status.
  • Expulsions are migrants denied exclusively through Title 42 to stop the spread of COVID-19. This status only applied from March 2020 to May 2023. USBP or OFO officers were empowered to expel people and return them to their home country or last non-US location. These individuals were not given the opportunity to apply for asylum.

These encounters don't necessarily reflect the actual number of people trying to cross the border; some multiple crossings during the same fiscal year, meaning they’d appear more than once in the data, and others successfully enter without encountering any US official.

How many border encounters occur each year?

Between October 2019 and January 2024, US Customs and Border Protection (CBP) reported over 9.8 million border encounters across the country. That’s roughly equivalent to the current population of Michigan, the 10th most populous state.

Monthly encounters peaked in December 2023, with over 370,000 people. Nearly 12,000 individuals were encountered at the border daily in December 2023, more than eight people every minute.

That month’s encounters alone were approximately 70% of the total encounters in 2017, which had around 527,000.

Embed on your website

Border encounters dropped slightly between March and April 2020, around the start of the pandemic, around when the Trump administration invoked Title 42 to authorize border expulsions in the interest of public health.

The Title 42 public health order ended in May 2023, so CBP officers could no longer expel illegal migrants for COVID-19-related reasons. Encounter numbers gradually rebounded over the remainder of 2020, surged 66% between February and March 2021, and have since remained elevated.

The CBP indicates that people processed under Title 42 had a higher recidivism rate than those processed under Title 8, so that may explain part of the increase in encounters during 2020-2023. According to the CBP, this higher-than-normal recidivism rate means "the actual number of unique individuals attempting to cross the border was substantially lower than total encounters."

Prior to this surge, the 2010s saw a relative lull in border encounters over the 2010s.

Embed on your website

Attributing the fluctuations in border encounters and migration to the US over time isn’t an exact science, but much of it comes down to push and pull factors.

Push factors are negative circumstances that drive people out of their countries of origin, like violence, insecurity, and famine in places like Guatemala, Honduras, and El Salvador. Pull factors are circumstances that make migrating enticing, including a strong economy, weak points in immigration enforcement, and a market for transnational smugglers who promise entry to the US.

How many people illegally cross the border?

While there isn’t any definitive data on undocumented immigrant numbers — there’s no way to know how many people entered the US without an encounter — border encounter numbers serve as a helpful if imperfect proxy. The at-the-border apprehension rate helps the Office of Immigration Statistics model what proportion of illegal entries are prevented by apprehensions.

Despite the relatively high number of encounters in 2021, the CBP’s estimated at-the-border apprehension rate averaged 78% from 2018 to 2020, compared to 35% from 2002 to 2004. This resulted in fewer entries without inspection than in the early 2000s.

The higher number of border encounters in recent years may be attributable to high apprehension rates, meaning that border patrol operations are working more efficiently, preventing a higher percentage of people from entering the country without authorization.

Embed on your website

From 2000 to 2012, with an apprehension rate under 50%, average annual unauthorized entries exceeded 1.4 million people nationwide; from 2013 to 2020, the average dropped to just over 190,000, coinciding with an increased average apprehension rate of 70.2%.

Preliminary estimates indicate that around 660,000 people successfully evaded apprehension while crossing the southwest border in fiscal year 2021.

Who is trying to cross the borders? 

According to the CBP, roughly 80% of people apprehended or denied entry between October 2019 and January 2024 were Latin American citizens. Nearly 30% came from Mexico, 9.1% from Guatemala, 8.9% from Honduras, 7.6% from Venezuela, and 5.8% from Cuba.

Embed on your website

Border encounters have risen since 2019 for all nations monitored by CBP, but the precise numbers vary over time based on each country’s unique political and economic dynamics, travel distances, and other factors influencing migration patterns.

Embed on your website

Not everyone who crosses into the US wants to immigrate permanently. Some people attempt to enter to carry out criminal activities like drug or human trafficking, or other smuggling-related acts.

How many border encounters involve children?

Between October 2019 and January 2024, at least 540,000 border encounters included children. The majority of child encounters, at 96.4%, are of unaccompanied children, with roughly 19,500, or 3.6%, made up of accompanied children.

Embed on your website

Within this period, nearly 70% of the people the CBP encountered were single adults. The proportion of encounters of individuals in family units nearly tripled between fiscal years 2020 and 2023 from 11.6% to 31.0% of total encounters. The number of family unit encounters also includes children traveling with their families, who are not included in the unaccompanied or accompanied children[1] categories.

How many migrants attempt to cross the southern border?

While border encounters occur all over the country, including via sea and air in states without international land borders, 81.7% of encounters from October 2019 to January 2024 occurred along the US-Mexico land border.

Texas had 47.7% of nationwide encounters along its border, followed by Arizona with 18.7% and California with 14.3%.[2]

Embed on your website

Where does this data come from?

All data included in this article comes from CBP data on nationwide encounters.

Nationwide encounters include the sum of CBP encounters across all areas of responsibility. This includes the northern land border, the southwest land border, the OFO non-land border ports of entry (such as airports and seaports), and the USBP sectors that do not share a land border (such as Florida or New York).

How does the Department of Homeland Security estimate illegal border crossings?

According to an August 2020 CBP report, the Department of Homeland Security estimates unauthorized border crossings by collecting data from various sources, including border encounters and refugee and asylee figures, as well as migrant sample surveys, interviews, and other statistical methodologies.

To estimate nationwide successful unauthorized border entries, USAFacts replicated the DHS data on Southwest Border entries without inspection using DHS data on the apprehension rate and CBP border encounters data, and applied the same methodology to national data.

Read more about immigration and border security in the US, including how many asylum seekers and refugees are coming to the US, and get the latest data by signing up for our weekly newsletter.

Nationwide Encounters
Last updated
July 18, 2023

The ‘accompanied minor’ category represents a child accompanied by a parent or legal guardian and the parent or legal guardian is either a US Citizen, Lawful Permanent Resident, or admissible noncitizen, while the child is determined to be inadmissible. This is distinct from the family unit, where at least one adult member is considered a noncitizen.


These border encounters also apply to ports of entry, such as airports or seaports.