Why can’t the U.S. Census ask a very simple question?

Should the 2020 U.S. Census ask about citizenship? Commerce Secretary Wilbur Ross decided that it should, and his decision triggered an explosion of legal challenges.
Last week, a federal judge in New York ruled that the question may not be asked. U.S. District Judge Jesse Furman wrote, “Secretary Ross’s decision to add a citizenship question to the 2020 census—even if it did not violate the Constitution itself—was unlawful for a multitude of independent reasons and must