President Donald Trump's newly-minted Homeland Security secretary, Markwayne Mullin, vowed on Wednesday morning to find nearly half a million "unaccounted for" kids, based on an internet conspiracy theory that misinterpreted a number about migrant minors.We're setting up a special department that's going over especially kids," Mullin told Newsmax's Rob Schmitt. "There was roughly 450,000 kids that are unaccountable, or unaccounted for under the Biden administration."The idea that 450,000 migrant children were "missing" or "unaccounted for" under the Biden administration is a statistic that has been thrown around for years in right-wing circles; Mullin's predecessor, Kristi Noem, repeatedly cited the figure too. However, it's based on a misunderstanding of a statistic.According to the Minnesota Reformer, "Trump and members of his cabinet have talked about lost immigrant children since the 2024 presidential campaign, and cite a Homeland Security report from that year. But as PolitiFact and other outlets have previously reported, those statements distort the report’s findings. Looking at data spanning both the Trump and Biden administrations, from fiscal year 2019 to 2023, the report found Immigration and Customs Enforcement could not monitor all unaccompanied minors released from the agency’s custody. It didn’t say the children were 'missing' or 'lost.'"In other words, Mary Miller Flowers of the Young Center for Immigrant Children’s Rights told the Reformer, “That does not mean in any way that the child is missing. That means that paperwork largely has not been able to reach that child, or phone calls have not been able to reach that child.”Mullin was appointed after Noem was unceremoniously fired by the Trump administration, which was reportedly enraged over her shifting of blame for a $200 million taxpayer-funded advertisement that promoted herself.