Why the census shouldn’t try to count undocumented immigrants

The U.S. Constitution requires the federal government to conduct a national census every 10 years, a tally that is used to apportion various benefits among the states, including seats in the House of Representatives. It’s a difficult task, and a magnet for disputes. The first census, conducted in 1790, was done by federal marshals assigned to visit every home in their judicial district to count the numbers of free white men and white women, other free persons, and slaves. The enumerators came up with 3.9 million people (about the present-day population of the city of Los Angeles) scattered among 13 states and four territorial districts — a total that President George Washington and Secretary of State Thomas Jefferson, who oversaw the count, complained was too low. So from the very get-go the decennial census has been framed by controversy over its accuracy.