(CNN)Given his rhetoric demonizing undocumented immigrants and his promise to engage in mass deportations when he returns to the White House in January, it’s kind of shocking that deportations actually dropped in the four years Donald Trump was president.

It’s also surprising that President Joe Biden’s administration has kept pace and deported a similar number of people as Trump’s.

 Trump also authorized immigration raids at businesses, something his incoming “border czar,” former acting US Immigration and Customs Enforcement Director Tom Homan, said to expect more of after Trump takes office in January.

Appearing Monday on Fox News, Homan said Trump 2.0 will be like his first term but with more deportations.

“It’s going to be the same as it was during the first administration, it’s just a hell of a lot more of them because 10 million people are getting in this country illegally under the Biden administration,” Homan said.

Why did Obama deport more people than Trump?

During his first term, Trump also promised mass deportations. And he did deport a large number of people – more than 1.5 million – during his four years in office, according to Kathleen Bush-Joseph, a policy analyst at the Migration Policy Institute.

But that’s about half the 2.9 million deportations undertaken during Barack Obama’s first term and fewer than the 1.9 million deportations during Obama’s second term. It’s on par with Biden’s 1.49 million deportations, according to updated calculations Bush-Joseph shared with me. Those figures do not include the millions of people turned away at the border under a Covid-era policy enacted by Trump and used during most of Biden’s term.

There’s a lot of context needed to explain those figures. Biden’s deportations focus on the border, according to Bush-Joseph. The Trump and Obama figures included more deportations from the interior of the country.

Obama’s deportations focused on single men from Mexico, she said, whereas undocumented immigrants today are more likely to be traveling to the US from further afield and in family units. This complicates the process of returning them, not only logistically but also because many countries will not accept repatriations. Mexico has begun taking in people from different countries as part of an agreement with the Biden administration.

“Important context for any administration dealing with deportations is that the US immigration system is extremely outdated, overwhelmed and under-resourced,” Bush-Joseph said, noting that there are 1.3 million people in the US who have already received a removal notice but have not been deported.

Another factor that has reduced the number of deportations is that many local law enforcement agencies have stopped cooperating with federal immigration authorities, a shift that began during Obama’s presidency and was amplified during Trump’s term, according to David Bier, director of immigration studies at the libertarian Cato Institute.

Unintended consequences

Bier’s research has revealed that Trump’s tough approach during his first term had some unintended consequences.

For instance, rather than prioritizing the removal of people with criminal records, Trump widened his dragnet by putting less emphasis on immigration action against people who were deemed public safety threats and instead prioritizing action against everyone in the country illegally. This led to Trump’s controversial family separation policy.

Bier argues that by filling detention centers with asylum-seekers rather than focusing on detaining people thought to have criminal histories, the Trump administration ended up allowing more people with criminal histories into the country.

In a separate study, Bier also looked at the rise in detention of people who crossed the border illegally during Trump’s term and found that it did not substantially raise the number of deportations.

Operating at capacity

While Trump is sure to authorize the kind of raids that will get public notice and include deporting people who have family members in the US, the system is so overwhelmed right now that Trump’s actions may not lead to a dramatic uptick in deportations.

Creating a system of camps to accommodate some portion of the more than 11 million people Trump says he wants to deport would dwarf the current total federal and state prison population, to say nothing of the cost of detaining so many people while they have their day in court.

“The idea that they’re going to be able to quickly set up the infrastructure to carry out deportations by the millions is just fantasy thinking,” Bier told me.

‘You’re talking about families’

John Sandweg, a former acting director of ICE during the Obama administration, said on CNN last week that ICE currently has about 41,000 beds in detention centers. He said a major concern is that Trump might try to find ways around the overwhelmed court system to deport people without a hearing.