There is a crisis on America’s border with Mexico.

The number of people arriving there has skyrocketed in the years since the pandemic, when crossings fell drastically. The scenes coming from the border, and from many US cities that have been touched by the migrant crisis, have helped elevate the issue in voters’ minds.

But for all the attention the topic gets, it is also widely misunderstood. The last few decades have seen a series of surges at the border and political wrangling over how to respond.In the latest effort to stem migration, President Joe Biden is expected to issue a controversial executive order Tuesday to temporarily shut down the border to asylum seekers whenever border crossings exceed 5,000 in a week or 8,500 in a single day.

Even if the policy survives court challenges, however, it will not address the root causes of migration and why the US has long been ill-equipped to deal with it, two issues that have been consistentlyoverlooked. Understanding all of that is key to fixing the problem.

Yes, border crossings are up. But the type of migrants coming, where they’re from, and why they’re making the often treacherous journey to the southern border has changed over the years. The US’s immigration system simply was not designed or resourced to deal with the types of people arriving today: people from a growing variety of countries, fleeing crises and seeking asylum, often with their families. And that’s a broader problem that neither Biden, nor any president, can fix on their own.

Here’s an explanation of the border crisis, broken down into eight charts.

The reality at the border has fundamentally changed in the years since Biden took office.

Former President Donald Trump effectively shut down the border during the pandemic. He instituted the so-called Title 42 policy, which expelled asylum seekers under the pretext of protecting public health.

As the pandemic subsided, migrants started attempting anew to cross the border in the last year of Trump’s presidency. When Biden won the 2020 election on a pro-immigrant platform, many migrants reportedly assumed (and were advised by smugglers) that his policies would be more welcoming, resulting in a sharp increase in crossings.

That assumption proved faulty. Biden maintained Trump’s Title 42 policy for more than two years after taking office, ending it only in May 2023 when he also terminated the national emergency related to the pandemic. Border encounters climbed even higher that fall. By December, immigration authorities recorded a record number of more than 300,000 migrant encounters. The number of encounters has been so high that it’s clear more people have been coming under the Biden administration than during the Trump years, even accounting for seasonal fluctuations in migration.

(Note: The same person can account for multiple encounters if they attempt to cross the border and come into contact with officials more than once. While the Title 42 policy was in place, migrants were not penalized for attempting to cross the border multiple times, and many did, though it’s hard to say exactly how many.)

In recent months, however, that trend has started to slow for a few reasons.

The Biden administration has instituted its version of Trump’s asylum transit ban. That rule allows immigration enforcement officials to turn away migrants for a number of reasons: if they do not have valid travel and identification documents, if they’ve traveled through another country without applying for asylum, if they don’t show up at a port of entry at an appointed time, and more.

More so than Biden’s asylum policies, the biggest factor in declining border encounters by far is Mexico’s efforts to step up enforcement, said Aaron Reichlin-Melnick, policy director at the American Immigration Council. Mexico has prevented some migrants from traveling north, bused and flown others back to Mexico’s southern border with Guatemala, and recently reached an agreement with Venezuela to deport its citizens.

That has made this spring so far the quietest at the US southern border in four years. There is a question, however, of how long this can last — and at what cost to asylum seekers.

“Despite Mexico going through the cycle of periodic crackdowns, none of them has lasted for longer than a few months or produced sustained, yearslong drops in the number of migrants arriving at the border,” Reichlin-Melnick said. “That’s why I call it a Band-Aid.”

The last time the US immigration system was significantly reformed in the late 1980s, migrants arriving at the border were primarily single adult males from Mexico looking for work. That is no longer the case.

More people are arriving at the US southern border intending to apply for asylum than ever before. That means instead of coming here claiming to look for work, they are seeking refuge because they have what the US government determines is a “credible fear” of persecution in their home countries on account of their race, religion, nationality, political opinions, or membership in a “particular social group,” such as a tribe or ethnic group.

The number of asylum applications filed as part of immigration court proceedings — where migrants encountered at the border are often referred after being found to have credible claims for protection — skyrocketed in recent years through the end of 2023.

Under the Trump administration, most migrants arriving at the southern border were from Central America’s “Northern Triangle”: Guatemala, Honduras, and El Salvador.

In the last few years, however, the number of migrants coming from those countries has been eclipsed by those coming from South America — particularly Venezuela, Colombia, and Nicaragua — and the Caribbean, including Haiti and Cuba. They have been driven out by recent compounding political and economic crises and natural disasters in their home countries.

Mexican nationals are still showing up at the border, but rather than coming for economic reasons, they’re being driven out by shifting patterns of cartel violence.

Migrants are increasingly coming from much more far-flung areas of the world. Migrants from China are among the fastest-growing populations at the southern border. There is also rising migration from India and Europe. Smugglers at the southern border have started marketing their services to these populations in a bid to expand their business.

More families are also coming. This might be due to the correct perception that families have a better chance of remaining in the US if they travel together than if they travel separately.

All of this seems to reflect the understanding that, for many of these migrant populations, there are no other good options but to go to the southern border, even if they may qualify to enter the US legally by other means. US refugee resettlement typically takes years. Wait times for some family-based green cards for some countries can take decades.

“There’s an increasing number of people that need protection, and they view that the fastest and clearest way to protection is to go to the US-Mexico border,” said Ariel Ruiz Soto, a senior policy analyst at the Migration Policy Institute.

The US immigration system is not designed to process so many people arriving at the southern border, especially not from such a broad array of countries and as part of families.

That has created a variety of new challenges:

These challenges have deepened the immigration court backlog, which has grown to over 3 million cases. The immigration courts handle cases in which the Department of Homeland Security does not have the authority to deport an immigrant unilaterally, and they consider any potential relief from deportation for which they may qualify, including asylum and protections for victims of torture.

So far this year, resolving those cases has taken more than a year on average, during which time migrants may have been detained or released into the US.

This is despite the Biden administration’s efforts to slow the growth of the backlog, including removing cases from the docket that are not a high priority for enforcement and involve people who do not have a criminal record or have been in the US for a long time.

The Biden administration started processing more asylum applications as the pandemic waned, leading to an increase in grants and denials. However, because of a lack of resources in the immigration courts and at US Citizenship and Immigration Services’s asylum office, the number of cases that are not adjudicated or temporarily closed has gone up even higher.

Biden has tried a variety of different approaches to handling the asylum backlog, including marking more cases under that non-adjudicated status and proposing to change the processing rules to allow the government to more quickly expel people who are potentially ineligible to remain in the US. The thinking is that fewer people will be interested in crossing the border if they don’t expect to be able to spend years in the US before ever having to litigate their asylum claim.

But it remains to be seen if that’s really working.

Absent real solutions to these issues, border states started busing migrants from the border to blue cities in 2022. Some of those cities, many of which have been sanctuaries for undocumented immigrants over the years, have implemented policies to evict migrants from public shelters after a certain period of time due to a lack of capacity. That even these pro-immigrant cities are struggling indicates how stressed the system has become.

Biden has also started sending more migrants, most of whom have no criminal record, to US Immigration and Customs Enforcement detention. The number of immigrants in ICE detention was at historic lows during the pandemic due to public health concerns associated with confining people in close quarters.

But that changed when the pandemic subsided and the number of people arriving at the border increased, creating both real and perceived pressure for the government to increase its capacity to detain migrants, said Tom Jawetz, former deputy general counsel at the Department of Homeland Security. At Biden’s urging, Congress raised the number of authorized ICE detention beds from 34,000 in fiscal year 2023 to 41,500 in 2024, close to historical highs.

The challenges at the border and throughout the immigration system have led more Americans to sour on immigration itself. A long-running Gallup survey has shown that, of late, Americans increasingly want to see immigration levels decrease.

Jawetz said that Americans’ dissatisfaction with the immigration system is “totally fair.”

“The immigration system is not working as you might want it to work. And that’s what people have meant for many, many years when they said the immigration system is broken,” he said.

That dysfunction predates Biden, but has now compounded to the point that members of both parties recognize the status quo is untenable. Most recently, a solution seemed within reach when a bipartisan group of lawmakers reached a deal that traded sweeping border security measures for aid for Ukraine, Taiwan, and Israel. But Republicans in the House ultimately tanked the bill so that Donald Trump could keep the issue alive on the campaign trail this year.

The fact is that responding to the global surge of migration requires major reforms that no one president could enact unilaterally. That includes providing adequate resources to the most overburdened parts of the system, ensuring the Border Patrol officers can perform more inspections, and staffing enough asylum officers and immigration judges to process migrants’ claims for protection.

By itself, enforcement is insufficient to resolve the problems at the border, Ruiz Soto said.

“Even the most strict policies of a potential future Trump administration would not be enough if the resources and infrastructure continues to be the same,” he said.

Update, June 3, 3:10 pm ET: This story has been updated with information on Biden's anticipated executive order to shut down the border.

Correction, May 14, 3:20 pm ET: This story, originally published May 12, included a chart on the Biden administration’s use of detention of migrants that initially underrepresented the policy by only depicting the number of migrants detained who had been arrested by Immigration and Customs Enforcement and not those arrested by other organizations like Customs and Border Protection. The full numbers are now depicted.