"I'm not sure where the president got his numbers," said Dave Ray, a spokesman for the nonprofit group FAIR, the Federation for American Immigration Reform, which advocates for lower immigration numbers.
Neither the White House nor the Department of Homeland Security responded to questions Tuesday about where the $250 billion estimate had come from.
The Heritage Foundation, for instance, estimated in 2013 that households headed by immigrants living in the U.S. illegally impose a net fiscal burden of around $54.5 billion per year.
And even Trump himself has contradicted the figure. During his 2016 campaign, Trump claimed that illegal immigration cost the country more than $113 billion a year — less than half the number he tweeted Tuesday.
That estimate appeared based on a paper by FAIR, which released an updated report in 2017 that claimed taxpayers "shell out approximately $134.9 billion to cover the costs incurred by the presence of more than 12.5 million illegal aliens, and about 4.2 million citizen children of illegal aliens" at the federal, state and local levels, with "a tax burden of approximately $8,075 per illegal alien family member and a total of $115,894,597,664."
The $116 million figure included services like health care and education, as well as spending on agencies like U.S. Immigration and Customs Enforcement, minus the $19 billion the group concluded those who are living illegally in the country pay in taxes.
But it also included costs associated with the children of those immigrants in its tally, even when they are U.S. citizens. The estimate was criticized for making broad generalizations and other major methodological flaws.
Michelle Mittelstadt of the nonpartisan Migration Policy Institute said that advocacy groups' numbers on both sides of the issue are notoriously flawed because "they don't look at the other side of the ledger."
"Doing a rigorous analysis that fully captures costs and economic contributions to come up with a net fiscal impact is quite complicated, because it is far easier to assess the cost side of the ledger, particularly uncompensated medical care and education, than it is to capture the full economic activity generated by unauthorized immigrants," she said via email, pointing to "their roles not just as workers and taxpayers but also as consumers."
The nonpartisan Pew Research Center also released new estimates last week that there were 10.7 million unauthorized immigrants living in the U.S. in 2016, down from a peak of 12.2 million in 2007 — less than groups like FAIR project.