Immigration and Border Control Explained: What Americans Need to Know

The number of arrivals at the southwest U.S. border has seemed to swing wildly over the last few years. Is this something we should expect in the future? Or do such swings prove that the United States has tools at its disposal to significantly affect the numbers of those seeking entry at the southwest border?

Shelly Culbertson Migration trends at the southwest border have varied significantly. The last time that there was a big spike of migrants at the border—in 2000—there were roughly 1.6 million encounters between Customs and Border Protection (CBP) agents and noncitizens without prior authorization to enter. These numbers then dropped; from about 2010 through 2018, encounters were roughly 400,000 per year or fewer. Encounters have grown significantly between 2018 and the start of 2024, with 2.5 million encounters in 2023, a historic high—and decreased again in the spring. Who is coming across the border has also shifted significantly over time. In early 2000s, it was primarily single adults from Mexico; in the 2010s, Mexico and Northern Triangle (Guatemala, Honduras, El Salvador) accounted for the vast majority of all encounters, with growing shares of families and children. In 2023, by contrast, less than 50 percent were from those countries, and the share of families and children grew even more.

Elina Treyger Policies that make it harder to enter the country—such as the measure that went into effect recently restricting paths into the country for asylum-seekers—can certainly affect how many people will enter the country. But they are not the only thing that matters.

Migration is a complex phenomenon that is shaped by many factors. People are pushed to migrate by violence, political repression, economic circumstances and dislocations, as well as natural disasters. The United States is an attractive destination because of its commitment to the rule of law, economic opportunities, existing immigrant communities and, for many, geographical proximity. These factors can be powerful, even if certain paths become more difficult. When some paths into the country become more costly, at least some migrants will shift to other paths. For example, making it more difficult to enter the country through claiming asylum might increase unlawful border crossings and human smuggling, as migrants try to evade detection. So, when the border appears under control, we should never assume that we got the policy mix “right” once and for all.

Can collaborating with neighboring countries help the United States manage migration flows?

Treyger Cooperation with Mexico and other Central and South American countries is indispensable to managing migration. Mexico is crucial. To state the obvious, the migrants coming to the southwest land border have all passed through Mexico or are Mexican. Many of the migrants have entered Mexico illegally. According to news media reports, Mexico stepped up enforcement efforts and is stopping three times as many migrants crossing its southern border in 2024 as it did in 2023. These stops contributed to the significant decrease in encounters at the U.S.-Mexico border in 2024.

Some of the policy tools employed by the United States to reduce the numbers of migrants paroled into the country as they wait for the outcome of their asylum claims—such as the Migrant Protection Protocols—require asylum-seekers to wait in Mexico. This, too, requires Mexico's cooperation. Cooperation with other major sending countries—many of which are in Latin America—is also vital if the United States wants to be able to repatriate their nationals. Not all countries agree to accept the return of their nationals.

Cooperation is also vital to address, in the sending countries, the root causes of migration: violence and instability, economic distress and inequality, corruption, powerful organized criminal organizations, and more. This may not produce clear effects in the short term, but it should be a crucial part of effective migration management.

What's happening with the surge of asylum-seekers, and how might that system be updated?

Culbertson According to CBO estimates, an estimated 6.5 million migrants crossed the U.S. southwest border since 2020—detected or not—and a majority of them have requested asylum. Most of those who were detected by CBP at the border were allowed to enter and stay in the country while waiting for an immigration hearing. Because of the large numbers of claimants and immigration courts that lack the capacity to process them in a timely way, court dates on average are more than four years in the future. Best estimates are that only in a small fraction of these cases are the migrants who are granted asylum.

This situation has several implications. First, for people truly in need of asylum, their claims take too long. The United States has legal and moral obligations to be a place of refuge. Second, some have argued that the long wait for court dates has incentivized economic migrants and others without strong asylum claims to use the asylum system for access to work opportunities.

In order to make the system more efficient and fair, offering asylum to those who need it, while disincentivizing use of the asylum process for other migration motivations, requires that the set of federal agencies responsible for border control and immigration processing be given sufficient resources to reduce these wait times. Only then would the people who need it get relief faster, and the people who don't qualify will be less incentivized to use the asylum system.

How well are U.S. refugee resettlement programs working? Are there changes needed to better support refugees and integrate them into American society?

Culbertson Refugee resettlement is a process by which refugees that are hosted in other countries around the world apply for resettlement in the United States, waiting in the other countries until they are granted approval to enter the United States. The top countries for refugees resettled in the United States are the Democratic Republic of Congo, Syria, Afghanistan, and Myanmar. After a thorough vetting process involving the U.S. State Department and the Department of Homeland Security (DHS), the United States resettles refugees through a process that involves coordination with local refugee resettlement agencies, which help the newcomers find housing, gain employment, and access public services such as health care and education.

The United States accepts a larger number of refugees for resettlement than any other country, but the numbers are small. For the more than 40 years of the refugee resettlement program, the United States has accepted an average of 73,000 refugees per year.

What are the alternatives to detention for individuals awaiting immigration proceedings, and how can these alternatives be effectively implemented?

Treyger Most of the noncitizens who are paroled into the country to await a decision on their case by immigration judges are not going to be detained. That is because the number of noncitizens who are paroled into the country exceeds the space DHS has available to detain them—even if the government wanted to detain them all. But that doesn't mean that there is no government supervision at all over these noncitizens. A growing number of them are placed into alternatives to detention (ATD) programs. ATD programs typically offer more intensive supervision than other conditions of release (such as GPS tracking), and/or various support services (“case management”) to the noncitizens. The purpose of ATD programs is to ensure that migrants comply with the law and show up at their immigration court hearings. ATD has been attacked from both sides: Some see it as an ineffective “catch and release” policy, while others view it as traumatizing to a vulnerable population and pointless. However, when ATD is tailored to address the participants' basic needs and to offer the level of supervision appropriate for each individual, it can actually be a valuable and viable tool of managing migration.

What should be the priorities for the next administration in responding to humanitarian crises at the border?

Treyger One key priority in responding to humanitarian crises should be to prevent such crises from happening in the first place—or at least lower their magnitude, insofar as possible. This may sound glib, but crises at the border often occur when there is a surge of migrants—and, in particular, migrants with specific characteristics, like family units, unaccompanied children, or migrants arriving from an uncommon point of origin—and DHS is simply not prepared to process them. It is, in large part, a resource issue: When large numbers of migrants show up at the border, DHS needs to have the capacity to surge resources to process them.

Surge capacity is not the only thing that matters, of course, but it is a necessity no matter what the policy is with regard to the arriving migrants. That is, DHS needs resources to both allow migrants to stay (under whatever conditions) and to repatriate them. Even if the chosen policy solution to a given crisis is to repatriate most, unless they are able to return to Mexico on their own, this requires flights and detention space (pending repatriation), which conforms to U.S. laws about the detention of children and families.

And what about the influx of unaccompanied minors?

Culbertson Significant numbers of children have been crossing the U.S. southwest border, as undocumented and asylum-seeking children, both unaccompanied and within families. Our 2021 RAND study found that from FYs 2017 through 2019, 575,000 children were encountered at the southwest border and 321,000 of them enrolled in U.S. schools in 2020. California, Texas, Florida, New York, Virginia, Maryland, New Jersey, Georgia, North Carolina, and Louisiana together hosted about 75 percent of the recent arrivals. The numbers of just the unaccompanied children encountered at the border over the past decade has generally increased, with about 44,000 in 2015 to a high of 152,000 in 2022. Encounters at the border have grown. Federal law guarantees a public education for all children in the United States regardless of immigration status. Our study found challenges related to offering enrollment for children at schools, addressing/managing/treating their trauma, providing English-language learning, as well as teacher training. Our study recommended developing curriculum materials for students with interrupted formal education, additional nonacademic supports (such as mental health or legal assistance navigating the asylum process), educational records transfer agreements with Central American countries, improved collaboration among federal and local agencies, additional funding for schools that receive large numbers of new students in a short period of time, and development of professionals with relevant language and other skills.

How does immigration impact the U.S. economy, and what policies could maximize the positive effects while mitigating any potential negative consequences?

Treyger Economic effects of immigration may be measured in different ways: on gross domestic product (GDP), GDP per capita, the national deficit, unemployment, wages, state and local budgets, and so on. And the effects on all these economic indices are not uniform. The Congressional Budget Office (CBO) has estimated (PDF) that the “surge” in immigration between 2021 and 2026 would have a net positive effect on the federal budget and the economy, as it “boosts federal revenues as well as mandatory spending and interest on the debt … lowering deficits, on net, by $0.9 trillion over the 2024–2034 period.” The impact on state and local budgets, however, varies across jurisdictions. And as CBO observes, generally, immigration is likely to raise state and local spending more than their revenues—although the impact on a given locality depends on its laws. Federal policies that might offset some of the costs to localities and mitigate these impacts would help spread the economic benefits of immigration more evenly.

Immigrants also contribute disproportionately to entrepreneurship and innovation. Research (PDF) shows that immigrants start firms at higher rates than the native-born, hold a disproportionate share of U.S. patents, and are robustly represented in frontier technology sectors. In an era of strategic competition, the United States may not be able to afford not to be welcoming of immigrants.

Culbertson Some 9 million immigrants arrived in the United States from 2021 to 2024. Some economists have estimated that it is the presence of large numbers of immigrants in the workforce that enabled the economic soft landing after the pandemic. After the pandemic, some 1.7 million Americans did not return to the workforce, and immigrants filled in, preventing a large workforce shortage. Immigrants have also contributed to half of the labor market's productivity growth during this time.

And yet, the United States still faces a worker shortage. There are 8.2 million job openings in the United States, in comparison with only 7.2 million unemployed workers. Because of declining birth rates, without immigration, the U.S. workforce would begin shrinking in 2040. The Congressional Budget Office estimates that, in the next decade, the economy will grow by $7 trillion more than it would without immigration.

At the same time, large numbers of new immigrants can also contribute to strains on local public services. For example, New York City has said that caring for its new migrants will cost $4.6 billion through 2025. And immigrants who have been paroled into the country to wait for their immigration court ruling are not legally allowed to work for a period of 180 days, making them either dependent on local public services and budgets or incentivizing them to work informally, under the table.

Can the United States reform legal immigration pathways to better match the needs of the labor market?

Treyger The United States can expand some of the immigration pathways available through employment—both permanent and temporary. Employment-based immigration channels (with a path to citizenship) are notoriously narrow, with numeric limits (140,000) that have not been updated in over three decades. Temporary employment-based visas are also limited in number and restricted to certain types of jobs, such as agricultural labor (H-2A visa) or high-skilled specialty workers (H-1B visa). These rigid limits simply do not allow employment-based migration to be responsive to the dynamic needs of the U.S. economy—to say nothing about their inadequate scale. Expanding lawful pathways for the economically motivated migrants would help meet the labor demand—and reduce the draw of entering the country unlawfully for at least some types of workers.

In what ways might climate change influence migration patterns, and how should U.S. immigration policy adapt to these changes?

Culbertson The vast majority of climate migration happens within countries, from people moving, for example, from rural areas to urban areas in the same country. At the same time, it is contributing and will contribute to some level of cross-border migration, but estimates vary widely. This is because of the range of estimates about the impacts of climate change on particular locations, as well as the range of estimates about how these impacts then influence people's decisions about where to live. By itself, climate change would rarely be a sole reason for migration. Societies adapt and mitigate risk by—for example—using better agricultural techniques or implementing improved building codes. Some people are not able to migrate because of poverty or infirmity. The World Bank estimates that by 2050, there may be between 44 million and 216 million internal climate migrants, with the wide variation reflecting scenarios relating to how societies develop policies to reduce climate change and mitigate the risks of climate change, and how individuals make decisions about where to live. Climate change also interacts in complex ways with other incentives for migration, such as economic opportunity, conflict, and the rule of law. People rarely attribute their reasons for migration primarily to climate change. Still, U.S. policy should work to mitigate risks of climate change both at home and abroad, and develop updated approaches to migration pathways in general.

What do you think are some of the major public misconceptions about immigration?

Misconception: (Illegal) Immigrants are criminals.

TreygerThere are many versions of this claim about immigrant criminality. Some claim that there are many criminals among those who are coming into the country unlawfully. The best data we have contradicts such claims. For example, CBP screens arrivals through various databases, and flags those with known criminal convictions in the United States and abroad. It probably doesn't detect all criminal histories, but it does detect a fair amount. Those numbers are relatively small: For example, if we're talking about people who try to cross the border unlawfully, less than one percent of all people apprehended by U.S. Border Patrol in FY 2023 had criminal records. Studies that examine a broader sample overwhelmingly conclude that first-generation immigrants (including those who are here legally and those who crossed the border illegally or are undocumented) are less likely to commit crimes than the native-born: For example, this recent study by a team of economists finds that “immigrants today are 60 percent less likely to be incarcerated” than the native-born. Of course, this doesn't mean that there are no cases of immigrants, including those who entered the country unlawfully, committing crimes. But the best evidence we have suggests they are less crime-prone than American citizens.

Misconception: It is feasible to “deport” everyone who is in the country illegally.

Treyger It would be so costly to deport all “deportable” individuals within the United States that it is virtually prohibitive. Deportations—or removals, to use a more current term—are not free. A removal is technically a “compulsory and confirmed movement of an inadmissible or deportable noncitizen out of the United States,” usually by Immigration and Customs Enforcement (ICE). The largest number of removals the United States has ever managed was just over 430,000 a year, in 2013. Estimates for the size of the unauthorized population hover around over 11 million. Estimates of the direct, monetary costs of deporting that many people are in the many billions of dollars: In 2015, the Center for American Progress estimated about $114 billion. For a sense of scale, the ICE budget for transportation and deportation (PDF) in FY 2023 was $420 million, and the total budget for detention was $3.4 billion. These cost estimates also do not include the cost to the U.S. economy of removing workers, or the harm to the social fabric from removing so many people who have U.S. citizen or resident family members. These costs are particularly significant because a lion's share of the unauthorized population has been here for over a decade—79 percent of this population entered prior to 2010, according to DHS estimates.

Misconception: Most immigration is illegal.

Culbertson Most immigration into the United States has been through legal visa processes, for purposes such as meeting the needs of the labor market and family reunification. There are some 36.9 million immigrants (naturalized citizens and green-card holders) in the United States. In 2022, there were an estimated 11 million unauthorized immigrants in the United States.

Misconception: Levels of immigration into the United States are new and unprecedented.

Culbertson The United States has always been a destination for immigration. Percentages of immigrants in the United States are at highs compared to recent decades—currently some 14 percent of the population in the United States are immigrants. While immigrants dipped to about five percent of the U.S. population in the 1970s, during the late 1800s and early 1900s, the percentage of immigrants in the population was similar to now, at about 15 percent.

Misconception: High levels of migration are a uniquely American situation.

Culbertson There are 281 million migrants globally, which is about 3.6 percent of the world's population. By way of comparison, in 1990, there were 199 million migrants, which was 2.9 percent of the world's population. Europe and Asia host 87 million and 86 million migrants, while North America has 59 million migrants. The percentage of international migrants are highest in Oceania, Europe, and North America. The vast majority of them have migrated legally, through regular visa processes. Some 15 to 20 percent are irregular migrants, meaning people who entered another country without prior authorization. Many of the world's wealthier countries have high numbers of irregular migrants, drawn because of strong economies and rule of law. In addition, there are 120 million refugees and asylum-seekers globally, an all-time high.

Misconception: The American public is divided between pro-immigration and anti-immigration.

Culbertson Virtually nobody opposes all immigration, just as vanishingly few favor completely open borders. Immigration is broadly supported by a majority of the U.S. population, although there are significant differences about the optimal numbers of immigrants, who can become an immigrant (for needed skills, say, or for family reunification), or under what means people should immigrate.

How can the next administration better utilize data and research to inform evidence-based immigration policies?

Treyger Accurate statistical data on immigration has been notoriously elusive. This is partly because different components of DHS and different federal agencies are involved in managing and tracking different aspects of immigration and immigration enforcement. And it is very difficult to combine all these disparate sources for a wholistic, coherent picture of the immigrant or noncitizen population and their characteristics. DHS made an important step towards improving the statistical evidence base when it created the Office of Homeland Security Statistics (OHSS) in 2023. One thing that OHSS does is systematically combine data from different parts of DHS to improve the ability of policymakers—as well as researchers like those of us at RAND—to support evidence-based policies. And statistical data alone is vital, but insufficient in and of itself to lead to better policies: Objective and nonpartisan research is needed as well.