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The government takes a census survey every 10 years. The bureau sends census takers and questionnaires to every U.S. household, though not everyone responds. In 2010, the government faced special challenges of counting transient families displaced by widespread mortgage foreclosures, non-English speaking immigrants fearful of enforcement raids and distrustful Americans opposed to government surveys.

Among the findings:

—Renters were undercounted by 1.1 percent, while homeowners were over-counted by 0.6 percent.

—Broken down by age, men 18 to 29 and 30 to 49 were more likely to be missed in 2010 than other age groups, while women 30 to 49 were over-counted; that is a pattern consistent with 2000. Adults 50 and older had over-counts of their population, while some young children ages 4 and under were missed.

—The District of Columbia had the highest shares of people who were missed, at 2.2 percent. West Virginia had the highest over-count of its population, at 1.4 percent.

Democrats and Republicans for years have disagreed on whether the census should be based on a strict head count or cross-checked against a “statistical adjustment” to include hard-to-track people, particularly minorities, who might have been missed.