On Tuesday, President Donald Trump tweeted (without evidence) that “illegal immigration costs the United States more than 200 Billion Dollars a year.”

Illegal immigration costs the United States more than 200 Billion Dollars a year. How was this allowed to happen? — Donald J. Trump (@realDonaldTrump) December 18, 2018

But two weeks ago, Trump was tweeting that “our Country loses 250 Billion Dollars a year on illegal immigration” and added that “Top Border Security … Pays for itself.”

Could somebody please explain to the Democrats (we need their votes) that our Country losses 250 Billion Dollars a year on illegal immigration, not including the terrible drug flow. Top Border Security, including a Wall, is $25 Billion. Pays for itself in two months. Get it done! — Donald J. Trump (@realDonaldTrump) December 4, 2018

Setting aside memories of Trump repeatedly promising — even as recently as August — that Mexico would pay for the border wall, much of the focus on that tweet from journalists and others centered on that $250 billion number. Namely, where on earth did that number come from, and what happened in two weeks that shifted that number down to $200 billion?

Some possible sources, from immigration restrictionists to (maybe) the White House?

President Trump’s use of numbers in his public statements and tweets has always been somewhat arbitrary. As Toronto Star reporter Daniel Dale, who fact-checks every single one of Trump’s public statements, put it in November, “If Trump cites any number at all, the real number is usually smaller.”

The $250 billion referenced in his tweet is a prime example, because in August 2016, Trump said during an Arizona speech that “illegal immigration costs our country more than $113 billion a year.” In Trump’s tweet from two weeks ago, he somehow more than doubled that number in two years, despite an overall downward trend in undocumented immigrants crossing the border, and then reduced that number by $50 billion for no apparent reason.

(I reached out to the White House and to the Department of Homeland Security for a source for the $250 billion number but have not yet heard back.)

In 2016, the source that Trump may have been referencing was a report by the Federation for American Immigration Reform, an organization that supports restrictions on immigration. That report, first published in 2013 and then updated last year, estimated that in 2013, the net cost of illegal immigration — which includes federal, local, and state taxes paid by undocumented immigrants — was $113 billion. In 2017, that number had increased, in FAIR’s estimation, to $115.8 billion. It’s worth noting that FAIR estimated that roughly 12.5 million undocumented immigrants are living in the United States, which is well above other estimates, like those of the Pew Research Center.

But $115 billion is notably not $250 billion, nor is it $200 billion. So where did Trump get these numbers? Perhaps from the White House website.

There’s a page on the site titled “It’s Time to End Chain Migration,” where the Trump administration laid out its opposition to family-based migration in December 2017. (For more on this issue, please read my colleague Dara Lind’s summary on how “chain migration” works.)

On that page, there is a graphic that argues “current immigration policy” is costing the United States $300 billion per year.

That number may have come from a 2016 report by the National Academies of Sciences, Engineering, and Medicine. According to a Washington Times article on that report, “Immigration drains the government, sapping as much as $296 billion a year from federal, state and local taxpayers while depressing wages, at least in the short run.”

The report also notes, “An immigrant and a native-born person with similar characteristics will likely have about the same fiscal impact.” In a PolitiFact interview with one of the report’s contributors, Gretchen Donehower of the University of California Berkeley, she said, “To characterize that one number” — $296 billion — “as the cost to current native-born taxpayers, is absolutely a case of cherry-picking one result out of a very detailed report.” And to be absolutely clear, that $296 billion number isn’t referring to just illegal immigration but to immigration, period, both legal and illegal.

And $296 billion “lost” on all forms of immigration to the United States still isn’t $250 billion lost on illegal immigration. And it’s not $200 billion lost on illegal immigration. And it’s not $113 billion lost on illegal immigration.

The search continues, again.