Where will you be on Census Day — living in your RV, couch surfing at your friends’, squatting in your parents’ basement?

The U.S. Census Bureau is preparing to count the more than 308 million men, women and children living in the country April 1, 2010. With just 10 questions on next year’s form, this would seem simple enough. Yet the count is likely to be not just the most costly but possibly one of the most difficult ever staged. “We are studying a population that is harder to count than the 2000 population,” census director Robert Groves told a group of journalists recently.

The lingering effects of the recession make it harder to find and count people. Millions of U.S. residents are now jobless or homeless — with no fixed address. One out of eight housing units is vacant nationwide; the rate in Washington state is about one in 20. Furthermore, an influx of immigrants — legal and illegal — over the past two decades make the counting that much tougher.

The Census Bureau realized in recent years that it missed significant numbers of new immigrants in the 2000 count — including many from countries where mistrust of government is common. That could again be a problem. For example, a group of Latino clerics has been urging illegal immigrants to boycott the census until Congress fixes the nation’s immigration laws. “The immigration raids have made some immigrants wary. They see census workers in that general way of being from the government,” said Sergio Romero, a professor at Boise State University who took a leave of absence to do community outreach for the 2010 census.

Among a broader group of Americans, there also appears a growing mistrust of the federal government’s reach after the 9/11 attacks and evidenced by the so-called Tea Party protests against economic-stimulus programs and health-care reform, Romero said. When he makes presentations about the census, Romero has been challenged by many of these skeptics. “Sometimes people will say, in their opinion, the federal government should not be collecting our personal information, but because it’s the law they will comply,” he said. “Others will state they will not complete the questionnaire. Period.”

The census, mandated by the Constitution, helps determine how more than $400 billion in federal funds for things like public housing, highways and schools are distributed to state and local governments. States have a big incentive to get the count right: Each uncounted person means a loss of about $1,400.

Census results are also used to determine how many members of Congress each state gets, as well as draw new political boundaries. Unlike in 2000, the U.S. government will bear the lion’s share of census costs, expected to reach roughly $15 billion. Cities and states, saddled with budget deficits, have little or no money to reach their own populations. Washington, for example, has no money to devote to the 2010 count. Seattle will spend only about $10,000 this year and an unknown amount next year.

Like the state, the city is planning some cheaper ways of urging people to fill out their census forms. Those include flashing reminders of the census on highway signs or inserting reminders into utility bills.

State and local governments have established complete-count committees, and the Census Bureau has formed partnerships within local communities to help raise awareness — particularly in hard-to-count areas where there are high concentrations of renters, immigrants, single men between 18 and 24, noncollege graduates and college students. “Our biggest problem will be getting good response from each household,” said Michael Burns, deputy regional director for the bureau. “Some people might be reluctant to put someone on their questionnaire if they are just sleeping on the couch. Or if it’s an uncle from Italy who came over on a tourist visa and decided to stay, living in the house, they might be scared to put him on the questionnaire.”

Census forms will be available in six languages — Russian, Chinese, Korean, Vietnamese, Spanish and English. For the first time, the agency will mail out forms in Spanish to 13 million households, including to two neighborhoods in Seattle.

The recession and growing joblessness present difficult challenges about how to count people where they live. Many people have lost their homes in this recession and are now doubling up with relatives, living in RVs or in shelters. “We expect the number of people in homeless situations to go up as a result of the economy,” Burns said. “Homeless providers and advocates are seeing people now that they’ve never seen before.”

Over a three-day period in late March, canvassers will attempt to count those who are in shelters and at mobile food vans and soup kitchens. Based on information they obtain from homeless-service providers, canvassers on the final day will go out in search of those living in outdoor locations, such as under bridges, along riverbanks, and — for the first time — living in their cars.