There has been much talk lately about how politics complicates the 2010 Census. (See this, this, and this.) Politics aside, it’s a daunting task to count each of the nearly 308 million residents of the United States once and only once. Some people are inevitably missed, while others are counted twice.

The 2000 census actually double-counted (about 11.6 million) more than it undercounted (10.2 million). Duplicates included “snowbirds” who spent part of the year in a second home, as well as college students and those in the military or prison. For the 2010 census new efforts are in place to limit double counting, including a printed warning on the form and a scanning procedure to find duplicate names and birth dates on completed questionnaires. While over-counting is a problem, it’s easier to deal with than undercounting.

The Census Bureau would rather weed out duplicates after the fact than risk missing people altogether, and so it conducts national advertising blitzes to convince everyone that “It’s in our Hands,” while investing extra resources in communities with people who are less likely to fill out their forms. State and local governments are making similar efforts, too, including the District of Columbia, Maryland, and Chicagoland.

Who is risk of being missed and where do they live? The Census Bureau has developed a “hard-to-count” score for every neighborhood in the country, based on 12 factors that are typically correlated with low response rates: rental and multi-family housing, overcrowding, unmarried individuals, low education and income levels, public assistance, high unemployment, recent movers, lack of phone service, linguistic isolation, and vacant housing units.

Paul Overberg at USA Today recently published a map showing hard-to-count scores for all counties in the U.S. Working for the Metro Program, naturally I wondered which metro areas were going to be most at risk. So I calculated the percent of each metro area’s population that lived in a “hard-to-count” neighborhood (see map). Here’s what I found:

 Jill Wilson map of Census Bureau data

Among the top 20 hard-to-count metros, only three (Albany, GA, Yakima, WA, and New York, NY) are not in a state bordering Mexico. The top sixteen are in TX, CA, NM, or AZ, though not all are border metros, with a cluster in California’s “inland empire.” Three metros (McAllen, Laredo, and Brownsville, TX) have more than half of their population in hard-to-count neighborhoods, and another seven have at least one third. Among metros with at least 1 million people, Los Angeles, New York, Las Vegas, Miami, and Houston rank highest, with at least one in five residents living in a hard-to-count neighborhood.

These places have their work cut out for them. The foreclosure crisis and economic downturn mean that more people are displaced from their homes and/or “doubling up” with others. Meanwhile, immigrants and others may be more hesitant to provide the government with information than they were 10 years ago. To compound matters, state and local governments are dealing with large budget deficits that leave less money for outreach this time around. Getting an accurate count in 2010 is going to be a challenge, to say the least.

Too bad the Census is still six months away. If it were held now, we could hand out Census forms to the masses of people lining up for H1N1 vaccinations. No one gets a shot until they turn in their completed form. But then again, maybe it wouldn’t help if the people who are “hard to count” are also the ones who are “hard to vaccinate.”