The estimated population of unauthorized immigrants in the U.S. stands at around ** million people. Although the number has stabilized, the United States has seen a spike in migrant encounters in the last few years, with over * million cases registered by the U.S. Border Patrol in 2023. This is a slight decrease from the previous year, when there were over *** million cases registered. Due to its proximity and shared border, Mexico remains the leading country of origin for most undocumented immigrants in the U.S., with California and Texas being home to the majority.

Immigration and political division

Despite the majority of the population having immigrant roots, the topic of immigration in the U.S. remains one of the country’s longest-standing political debates. Support among Republicans for restrictive immigration has grown alongside Democratic support for open immigration. This growing divide has deepened the polarization between the two major political parties, stifling constructive dialogue and impeding meaningful reform efforts and as a result, has led to dissatisfaction from all sides. In addition to general immigration policy, feelings toward illegal immigration in the U.S. also vary widely. For some, it's seen as a significant threat to national security, cultural identity, and economic stability. This perspective often aligns with support for stringent measures like Trump's proposed border wall and increased enforcement efforts. On the other hand, there are those who are more sympathetic toward undocumented immigrants, as demonstrated by support for the Deferred Action for Childhood Arrivals (DACA) program.

In 2022, an estimated 10.99 million unauthorized immigrants were living in the United States. This is an increase from about 3.5 million unauthorized immigrants who lived in the United States in 1990.

This study was conducted to examine whether a rising crime rate in El Paso, Texas and San Diego, California in 1986 could be attributed to, among other factors, the influx of undocumented aliens. Variables include level of involvement of undocumented aliens in serious felony arrests in San Diego and El Paso Counties, the outcome of serious felony arrest cases involving undocumented persons compared to others arrested for similar offenses, the impact of arrests of undocumented aliens on the criminal justice system in terms of workload and cost, the extent that criminal justice agencies coordinate their efforts to apprehend and process undocumented aliens who have committed serious crimes in San Diego and El Paso counties, and how differences in agency objectives impede or enhance coordination. Data are also provided on how many undocumented persons were arrested/convicted for repeat offense in these counties and which type of policies or procedures could be implemented in criminal justice agencies to address the issue of crimes committed by undocumented aliens. Data were collected in the two cities with focus on serious felony offenses. The collection includes sociodemographic characteristics, citizenship status, current arrest, case disposition, and prior criminal history with additional data from San Diego to compute the costs involving undocumented aliens.

In 2024, there were nearly 240 thousand illegal border crossings detected at the borders of the European Union, with the Eastern Mediterranean route detecting the highest number of crossings, at 69,436.

We apply standard demographic principles of inflows and outflows to estimate the number of undocumented immigrants in the United States, using the best available data, including some that have only recently become available. Our analysis covers the years 1990 to 2016. We develop an estimate of the number of undocumented immigrants based on parameter values that tend to underestimate undocumented immigrant inflows and overstate outflows; we also show the probability distribution for the number of undocumented immigrants based on simulating our model over parameter value ranges. Our conservative estimate is 16.7 million for 2016, nearly fifty percent higher than the most prominent current estimate of 11.3 million, which is based on survey data and thus different sources and methods. The mean estimate based on our simulation analysis is 22.1 million, essentially double the current widely accepted estimate. Our model predicts a similar trajectory of growth in the number of undocumented immigrants over the years of our analysis, but at a higher level. While our analysis delivers different results, we note that it is based on many assumptions. The most critical of these concern border apprehension rates and voluntary emigration rates of undocumented immigrants in the U.S. These rates are uncertain, especially in the 1990’s and early 2000’s, which is when—both based on our modeling and the very different survey data approach—the number of undocumented immigrants increases most significantly. Our results, while based on a number of assumptions and uncertainties, could help frame debates about policies whose consequences depend on the number of undocumented immigrants in the United States.

In January 2022, it was estimated that about 1.85 million male illegal immigrants living in the United States were aged between 35 and 44 years old. In that same year, it was estimated that 1.52 million female illegal immigrants living in the U.S. were between 35 and 44 years old.

In 2022, about **** million illegal aliens were apprehended in the United States. This was a significant increase from the previous year, when there were around **** million illegal aliens apprehended nationwide. Apprehensions refer to Border Patrol apprehensions and ICE administrative arrests.

In 2022, the greatest number of illegal aliens returned in the United States were from the Philippines, with ****** illegal aliens returned. India, Canada, China, and Russia rounded out the top five in that year.

Immigration enforcement has ambiguous implications for the crime rate of undocumented immigrants. On the one hand, expulsions reduce the pool of immigrants at risk of committing crimes, on the other they lower the opportunity cost of crime for those who are not expelled. We estimate the effect of expulsions on the crime rate of undocumented immigrants in Italy exploiting variation in enforcement toward immigrants of different nationality, due to the existence of bilateral agreements for the control of illegal migration. We find that stricter enforcement of migration policy reduces the crime rate of undocumented immigrants.

Acknowledgement

The following table is imported from the 2019 Yearbook of Immigration Statistics under the Department of Homeland Security:

The 2019 Yearbook of Immigration Statistics is a compendium of tables that provide data on foreign nationals who are granted lawful permanent residence (i.e., immigrants who receive a “green card”), admitted as temporary nonimmigrants, granted asylum or refugee status, or are naturalized. The Yearbook also presents data on immigration enforcement actions, including apprehensions and arrests, removals, and returns.

Table 33. Aliens Apprehended: Fiscal Years 1925 to 2019 (https://www.dhs.gov/immigration-statistics/yearbook/2019/table33)

Inspiration

The data was collected to observe trends in history reflecting the number of immigrants apprehended.

This dataset provides relevant figures concerning Mainland illegal immigrants apprehended and repatriated

Activists and politicians often express a belief that the language used to describe immigrant populations, such as “illegal” vs. “undocumented,” can impact policy opinions. Existing experimental studies, however, have found relatively little support for that conjecture. In this note, we extend this line of research by exploring whether language impacts perceptions about unauthorized immigrants, such as their association with criminal behavior. Our study uses a conjoint design with experimentally manipulated instructions: respondents are randomly asked to identify profiles that belong to “illegal” or “undocumented” immigrants. We find that language used in the conjoint instructions does not impact perceptions about unauthorized population. At the same time, our observational results show that respondents’ preferences for terms “illegal” and “undocumented” are related to attitudes toward immigration. We discuss the implication of these results for the debate regarding the role of labels in political conflict over immigration.

From January to June 2025, the highest number of illegal immigrants that arrived in Spain via land and sea came from Mali, with approximately ***** people. The immigrants from Senegal and Algeria were the second and third most numerous group, with ***** and ***** people leaving their country of residence, respectively. More than ****** illegal immigrants reached the Iberian country in 2024. A risky journey Spain, together with Italy and Greece, are the main points of entry to Europe for illegal migration. Most arrivals happen through the Mediterranean Sea, which is a very dangerous journey for migrants. While active since 2006, the migration route from the coasts of West Africa to the Canary Islands (the closest territory of the European Union) has become particularly popular in recent years, even though so many people lost their lives their. Undocumented minors Among those reaching the Spanish territory are undocumented and unaccompanied minors, known in Spanish as "menas” (Menores Extranjeros No Acompañados). In 2018, the number of unaccompanied and separated children that arrived by sea exceeded *****, which represented the largest figure since at least 2014. This number decreased by approximately ***** cases in 2020. Nearly half of them came from Morocco, separated from Spain by merely ** kilometres of water at the Gibraltar Strait's narrowest point.