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Border Security

One of the most controversial and important topics in American politics is the security of its borders. Over the last two years, the system has been overwhelmed by large numbers of entrants. How does the U.S. government protect its borders? Why are we experiencing such an increase in border activity?

How many people enter the U.S. without authorization?

Pre-pandemic estimates of the number of unauthorized immigrants living in the U.S. calculate the number as slightly more than 11 million. Analysis by Policy vs Politics included in the chart below shows that the number has increased to about 16 million by 2023. (For details and sources for this chart, see our policy brief on Unauthorized Immigration linked in the references section at the end.)

Source: Analysis by Policy vs Politics from DHS (2022), Gramlich (2023), and Soto (2022)

For our 2023 estimate, Policy vs Politics analysts used the average of 2018-era estimates as a baseline, subtracting the Department of Homeland Security (DHS) estimate of the number of undocumented who left the U.S. during 2018 – 2023 and adding (a) the DHS estimate of the number of new illegal entrants during 2018 – 2023, (b) the number of refugees admitted in the same time, and (c) the number of individuals in the U.S. who have asylum claims pending as of late 2023. It is important to recognize that people in the last two categories (refugees and those with pending claims) are legally in the U.S.. However, their large numbers undoubtedly contribute to public perceptions of the size of the undocumented population.  

Three policy changes have led to increased admissions of asylum seekers. The first was the repeal of the Migrant Protection Protocols (more commonly known as the “Remain in Mexico” policy). This policy was created by the Trump administration in 2019 and later canceled by the Biden administration in 2021. It required asylum-seekers to wait in Mexico as their cases went through U.S. immigration courts, where they lived in makeshift refugee camps and were often vulnerable to crime.   

The second policy change was the establishment of Temporary Protected Status (TPS). DHS can give the TPS designation to countries experiencing political, economic, or environmental upheavals. It allows individuals from these countries to enter the U.S. and receive work authorizations. The TPS designation for a country lasts up to 18 months but can be extended. Countries like El Salvador, Haiti, Honduras, Ukraine, and Venezuela have been given TPS status in recent years. Many of these entrants have also applied for asylum, allowing them to remain in the U.S. indefinitely. 

The third policy change, the parole system, was made because of the government’s inability to house large numbers of entrants at the border. Now, many of these individuals are released into the care of relatives and nonprofit organizations throughout the nation while their claims are adjudicated. Typically, their living expenses are covered by local, city, and state tax revenue, although those with TPS status can obtain work authorization. The federal government pays some transportation costs, although some states bordering Mexico have arranged transportation for asylum seekers to cities in northern states. 

The reality of the current system is that many entrants will legally live and work in the U.S. for extended periods (years) while their claims are being adjudicated. An additional concern is whether those on parole will show up for court dates or leave the U.S. if their claims are denied. 

Where are entrants coming from?

Historically, most of the documented and undocumented entrants at the southern border were single individuals (usually young men) from Mexico entering the U.S. to pursue economic opportunities. These individuals typically stayed in the U.S. for relatively short periods (less than five years) and then returned to their home countries. A separate flow of entrants came from Cuba, taking advantage of U.S. laws that grant permanent residence status to any Cuban who arrives by whatever means on U.S. soil (the so-called “feet dry” rule).

This situation has changed in recent years. The new entrants are more likely to want to stay in the U.S. permanently rather than for a short period. There are more unaccompanied minors and families with children. Current entrants also arrive from a wider range of countries, mostly those from countries with a TPS designation. In addition, while the feet-dry rule no longer exists, the number of entrants from Cuba has increased because of a change in Nicaraguan visa policies that allows Cubans to travel easily to that country and then through Mexico to the U.S.. Significant numbers of  asylum seekers come from Afghanistan, where the U.S. fought with the government against Taliban forces from 2001-2021, and from Ukraine, where citizens face attacks by Russian forces.

How does the U.S. enforce its borders?

The U.S. monitors its borders through ground patrols, aerial surveillance (including drones), and advanced technology such as cameras, sensors, and biometric systems. The Customs and Border Protection (CBP) agency plays a central role in border monitoring. The CBP employs Border Patrol agents responsible for patrolling between ports of entry, while Office of Field Operations officers monitor the ports of entry. The CBP collaborates with other agencies, including Immigration and Customs Enforcement (ICE), the National Guard, and the Coast Guard, in these efforts. The budget for border security increased every year between 1990 and 2020 (from $262 million to $4 billion). 

The budget for overall border enforcement (including border security and operations within the United States) is much larger. The U.S. government spends about $15 billion annually on border enforcement, including the operations of CBP and ICE. This budget covers many activities, including the construction and maintenance of physical barriers, the construction and operation of surveillance equipment, salaries, and the arrests and removal of unauthorized immigrants. The 2023 budget includes $17.5 billion in funding for CBP, including a $1 billion investment in modern security technology. 

Barriers to block entry at the borders include physical structures such as walls and fences, many of which may be made from concrete and steel, while others, in some instances, utilize shipping containers, barbed wire, and other materials. Some construction is being organized and funded by bordering states such as Texas. Additionally, routine patrols using vehicles, aircraft, helicopters, and new technologies (cameras, drones, radar) are used to monitor the border. 

The entire U.S.-Mexico border is about 2,000 miles long, but the Rio Grande River is about 1300 miles of this length. Before President Trump took office, there were approximately 650 miles of fencing along the U.S.-Mexico border out of 700 miles of land border. Construction of fencing continued during the Trump administration. Under the Biden administration, there has been limited construction of new walls, renovation of existing barriers, and, in some cases, removal of physical barriers. There is ongoing litigation at both the federal and state levels, impeachment inquiries regarding the handling of border construction and removal of barriers, as well as the allocation and funding of resources, including the National Guard.

More recently, enforcement policy has emphasized surveillance technologies over physical barriers. One reason is that low-technology tools can be cost-effective and potentially as effective as physical barriers. Moreover, border walls redirect unauthorized immigration towards more dangerous areas, such as crossing the Rio Grande River or the desert. 

How does U.S. border security compare to other nations?

The U.S. has one of the world’s most extensive border enforcement regimes. However, U.S. border enforcement approaches are very different from those in other countries. Within the European Union, some regions have physical barriers and heavily militarized enforcement at their external borders. In contrast, others rely on policy measures such as bilateral readmission agreements with neighboring countries. For example, the EU works with Libya’s government to stop immigration through the Mediterranean by providing support for the Libyan Coast Guard. The EU also agreed with Turkey’s government that migrants attempting to enter Greece would be returned to Turkey. Additionally, countries like Australia employ maritime patrols and offshore processing of asylum seekers.

What are the consequences of changing current policies?

The reality of current border security is that the system is overloaded. Border agents must patrol a long, largely desert border to deter entrants. Experience suggests that physical barriers alone are not a deterrent. The simple fact is that coming to the U.S. represents a huge economic opportunity for individuals living in Central and South America, as well as other regions of the world. Although it is unclear under these conditions what measures would be sufficient to cut down on the number of illegal entrants, recent data suggests the current administration’s policies as perceived in the global community are giving more immigrants hope they will not be turned back on arrival at the U.S. border.

Ongoing negotiations in the U.S. Senate on revisions to border policies have focused on setting daily quotas for refugee-seekers. Sustained levels above these quotas would automatically suspend many current policies favorable to asylum seekers, including the TPS and parole systems. On the one hand, these policies would limit the number of people admitted to the U.S.. On the other, opponents of refugee admissions see the proposed quotas (5000 per day) as giving implied approval to entry levels that they see as unacceptably high. 

Quotas are unlikely to solve the border crisis regardless of where they are set. If refugees are turned away at the border, it is not clear where they will go. The strong possibility is that they would remain in refugee camps at the U.S.-Mexico border in the hopes that U.S. policy would change. U.S. and Mexican officials are currently engaged in ongoing meetings to develop joint initiatives to manage the refugee situation. Still, there is no assurance that these efforts will succeed. 

In sum, there are no easy, costless solutions to the situation at the southern border:

  • Adding immigration judges to decide cases will help reduce the backlog, but only over time, and may even encourage more people to try to enter the U.S..
  • Policies that require employers to verify new hires are in the U.S. legally force undocumented individuals to work on a cash basis and make them vulnerable to exploitation. 
  • Finding illegal entrants would require house-to-house searches and raises concerns about violating the civil liberties of U.S. citizens.
  • Ending the TPS and parole programs gives asylum seekers very few options: return to their home country and whatever problems prompted them to leave, live in a refugee camp in Mexico, or try to enter the U.S. illegally. 



Further Reading

Andreas, P. (2019). Crime, Violence, and Illicit Economies in Regional and Global Perspective. Perspectives on Politics, 17(2)., accessed 2/12/24.

Jones, R. (2023). Borders and Walls: Do Barriers Deter Unauthorized Migration? Migration Policy Institute., accessed 2/12/24.

Policy vs Politics Policy Brief: Refugees and Asylum, available at



How many people enter the U.S. without authorization?

Andreas, P. (2019). Crime, Violence, and Illicit Economies in Regional and Global Perspective. Perspectives on Politics, 17(2), 102-117., accessed 2/12/24.

Andreas, P. (2014). Smuggler Nation: How Illicit Trade Made America. The Independent Review, 18(4)., accessed 2/12/24.

Customs and Border Protection. (2024). Nationwide Encounters., accessed 2/12/24

Department of Homeland Security. (2020). Yearbook of Immigration Statistics 2020., accessed 2/12/24.

Department of Homeland Security. (2023). Department of Homeland Security Border Security Metrics Report: 2022., accessed 2/12/24.

Gramlich, J. (2023). Monthly encounters with migrants at U.S.-Mexico border remain near record highs. Pew Research Center., accessed 2/12/24.

Migration Policy Institute. (2019). Profile of the Unauthorized Population: United States., accessed 2/12/24.

Ruiz Soto, A. (2022). Record-Breaking Migrant Encounters at the U.S.-Mexico Border Overlook the Bigger Story. Migration Policy Institute., accessed 2/12/24.

How does the U.S. enforce its borders?

American Immigration Council. (2021). The 287(g) Program: An Overview., accessed 2/12/24.

Calavita, K. (2019). Inside the State: The Bracero Program, Immigration, and the I.N.S. International Migration Review 27(4), 895., accessed 2/12/24.

Department of Homeland Security. (2023). Fact Sheet: U.S. Government Announces Sweeping New Actions to Manage Regional Migration., accessed 2/12/24.

Durand, J., & Massey, D. (2019). Debacles on the Border: Five Decades of Fact-Free Immigration Policy. The ANNALS of the American Academy of Political and Social Science, 684(1), 6–20., accessed 2/12/24

Jones, R. (2016). Borders and Walls: Do Barriers Deter Unauthorized Migration? Migration Policy Institute., accessed 2/12/24.

Massey, D., Pren, K., & Durand, J. (2016). Why Border Enforcement Backfired. American Journal of Sociology 121(5), 1567., accessed 2/12/24.

Miroff, N. (2019). Smugglers are sawing through new sections of Trump’s border wall. The Washington Post., accessed 2/12/24.

Parsons, J. (2020). “Border Militias: Experience, Narrative, and the Moral Imperative to Act” Journal of Extreme Anthropology 4(1), 1-21., accessed 2/12/24.

Vina S., Nunez-Nerto, B., & Weir, B. (2006). Civilian Patrols Along the Border: Legal and Policy Issues. Congressional Research Service., accessed 2/12/24

How Does U.S. Border Security Compare To Other Nations?

European Parliament. (2023). Management of the external borders., accessed 2/12/24.

Terry, K. (2021). The EU-Turkey Deal, Five Years On: A Frayed and Controversial but Enduring Blueprint. Migration Policy Institute., accessed 2/12/24.

What Are The Consequences Of Changing Current Policies?

Felbab-Brown, V., & Norio, E. (2021). What Border Vigilantes Taught US Right-Wing Armed Groups. Brookings Institute., accessed 2/12/24.

Krogstad, J., & Gonzalez-Barrera, A. (2022). Key facts about U.S. immigration policies and Biden’s proposed changes. Pew Research Center., accessed 2/12/24.

Yayboke, E., Nzuki, C., & Myers, M. (2021). The Biden-Harris Strategy on the Root Causes of Migration (and Fragility) in Central America.’ Center for Strategic and International Studies., accessed 2/12/24.



Julia Acevedo (Intern) is a Political Science and Public Policy double major at Susquehanna University and is expected to graduate in May 2024. She is planning on pursuing a Masters degree in Public Health.

Elijah Oaks (Intern) is a student at Dartmouth College. He is expected to graduate in 2024 with a major in English and a minor in Religion. He is a Policy Fellow at The Cicero Institute.

Mary Adams (Team Lead) is a graduate student in the Department of Political Science at Indiana University and holds a MPA in Public Administration from Western Kentucky University. Her research is in American politics and political psychology.

Alexandra Fillindra (Subject Matter Expert) is Associate Professor of Political Science and Psychology at the University of Illinois Chicago. She received her PhD in Political Science from Rutgers University and specializes in American gun politics, political violence immigration policy, race and ethnic politics, public opinion, and political psychology. 

Nathaniel Birkhead (Content Lead) received his PhD in Political Science from Indiana University. He is Associate Professor of Political Science and Department Chair at Kansas State University. His research focuses on American politics, especially Congress and state legislatures. 

William Bianco (Research Director) received his PhD in Political Science from the University of Rochester. He is Professor of Political Science and Director of the Indiana Political Analytics Workshop at Indiana University. His current research is on representation, political identities, and the politics of scientific research.

Publication Log

Publication: January 30, 2024

Revision: February 22, 2024 

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