The Challenge of Finding People Before Counting Them

"[I]n New York City this task is incredibly difficult, and census response rates have chronically lagged behind the national average."

"In addition to its difficult housing landscape, New York City also has in spades just about every group that's statistically least likely to mail back a census questionnaire: young singles, African-American men, hundreds of thousands of public-housing residents, and an evolving mix of immigrants.

"Three million foreign-born people, 600,000 of whom have come since 2000," says Stacey Cumberbatch, New York City's census coordinator.

That 3 million is more than a third of the city's population — people who may not speak English and may never have heard of a census. Since the last count, New York's demographers have been trying to track the constant migration of various ethnic groups in, out and around the city."