In his first term, Trump wanted the U.S. Census to ask about citizenship. Critics worried that inserting the question would lower the response rate, leading to an undercount. In June 2019, the U.S. Supreme Court “ruled that Trump had not provided a sufficient rationale to add a citizenship question to the 2020 census as part of his broader campaign to stop illegal immigration.”

But that was then, this is now.

Science reports that the Trump administration scrapped plans to overhaul the census and inserted the citizenship question. The result, say knowledgeable insiders, will be an inaccurate census.

The U.S. Census Bureau spent 6 years preparing for a test this spring of ways to make the 2030 decennial census both more accurate and less expensive. In 1 day this month, the administration of President Donald Trump discarded many of those changes and replaced them with an approach researchers warn will likely do the opposite. That’s in part because the test will now include a citizenship question—something Trump has wanted to add since the previous census.

The agency originally planned to ask more than 650,000 residents in six test sites to respond to the same nine questions as on the 2020 census. But on 3 February, the Census Bureau posted a notice that “turned the plan on its head,” says Terri Ann Lowenthal, former staff director of a congressional panel that oversees the agency. In addition to paring down the sites to two, both midsize cities in the South, the agency said it would use some version of the much longer American Community Survey (ACS), an annual survey that monitors demographic changes and asks where residents were born and whether they are a U.S. citizen.

Taken together, the changes blow up the agency’s carefully crafted plans to better reach groups who are traditionally undercounted and to hold down costs, which reached $13 billion in 2020, says former Census Bureau Director and statistician Robert Santos. “It’s no longer a test of how to conduct the decennial census,” explains Santos, an appointee of former President Joe Biden who stepped down 1 month after Trump took office. “The changes make no sense and are not something the Census Bureau would have done on its own.”