Jorge Sanjuan pulled back a chain-link fence, and Cindy Quezada squeezed through the gap. They stepped over two rotting mattresses and an old tire and peered into a backyard. The neighbors eyed them suspiciously. “You guys with ICE?” one teenager asked.

Quezada laughed and shook her head. It was a sunny January afternoon, and she and Sanjuan had spent the past three hours crisscrossing the alleys of a Fresno, California, neighborhood with small one-story bungalows and Mexican restaurants, looking for sheds, garages, and trailers serving as makeshift homes. They weren’t out to harass the immigrants living there; they were there to count them.

Quezada and Sanjuan were working with the Central Valley Immigrant Integration Collaborative, a network of organizations embarking on a pilot program to identify “low-visibility housing” in Fresno in preparation for the 2020 census. The Constitution requires the executive branch to tally “the whole number of persons in each state.” But every 10 years, the census counts some people more than once—such as wealthy Americans who own multiple homes—and others not at all, particularly those who are poorer, move often, or […]