A modest system holding fewer than 3,000 migrants a day at the end of the 1970s, detention has now morphed into a sprawling machinery ensnaring immigrants across the country. And facilities operated under both Immigration and Customs Enforcement (ICE) and the Border Patrol continue to come under fire for holding people in squalid conditions with minimal access to hygiene and medical care.

While the population of people in detention has grown, so has the government budget to fund the beds to hold them. Billions of American taxpayer dollars are now allocated to support a system where for-profit companies hold the vast majority of immigrants. In fiscal year 2018, private prison companies like CoreCivic and GEO Group derived 25 percent and 20 percent of their profits respectively from ICE, which is now their biggest client. In the same year, ICE spent over $250 million on contracts with GEO Group and another $60 million with CoreCivic.

ICE also runs alternatives to detention programs, including electronic monitoring, phone check-ins and home visits. Over 98,373 people are currently on electronic monitoring, according to ICE. Where ICE pays several hundred dollars per person per day in detention, alternative programs cost an average of $4.42 a day.

With illegal immigration at the heart of the debate over U.S. immigration policy, the number of undocumented immigrants has grown from less than 1 million in the 1970s to just under 11 million today, about 3 percent of the U.S. population.

Although the number of undocumented immigrants has actually declined since 2007, the government is locked in a stalemate over how to deal with those still here and those who continue to arrive.

Even as the numbers held in detention have expanded, actual apprehensions at the U.S.-Mexico border by the Border Patrol and in the interior by ICE have fluctuated, declining over all since 2000, and spiking again this year. Trump administration enforcement measures have not deterred the most recent surge, made up mostly of Central American families fleeing instability and violence.

The number of detention facilities soared in the 1990s. Then, by 2017 the number declined as privately run facilities began to replace some of the smaller local jails.

Ten percent of detainees are in ICE-run facilities, 20 percent are in county and local jails, and the rest are in facilities run by private corporations. Though unaccompanied children are placed in facilities operated by Health and Human Services, over 500 children and parents are currently detained by ICE. And the Trump administration has made new efforts to remove the 20-day time limit for detaining migrant children.

As the race for the 2020 presidential election heats up, Democratic candidates have clamored to decry Trump’s immigration policies.

Nearly all candidates support an end to detention for asylum-seeking families. In Sen. Elizabeth Warren’s immigration plan, she promises to reserve detention for extreme cases of safety or flight risks. Sen. Bernie Sanders told the Washington Post, “We must promote and implement these cheaper, more effective and more humane alternatives to keeping children and families detained in overcrowded, understaffed and ad-hoc facilities.” Former Vice President Joe Biden also pledged to end the detention of children in a private meeting with BOLDPAC, a political action committee.

In the meantime President Trump continues to redirect funding from the Coast Guard and other agencies to a detention system whose daily population has grown by more than 40 percent since he took office. And it’s only getting bigger.