College of Liberal Arts & Sciences

College of Liberal Arts & Sciences

• Everyone counts
  

  Statisticians, including Song Chen, working to make population surveys a little more accurate.

  
  Just how accurate is the U.S. Census?
  
  While it comes close to estimating the true number of people in the nation, it has a way to go before it is more accurate.
  
  "The American population is very mobile," says Song Chen, associate professor of statistics. "One survey on a particular census date will give you a number. If you did another survey soon after that, people will move, die, leave the country, and you'll have a totally different number.
  
  "Another challenge of any population survey in this country is that the United States is not a homogenous population."
  
  Past U.S. Census reports showed minorities, renters, people in their 20s and other groups are harder to count because they are harder to find.
  
  Chen and fellow Department of Statistics faculty members Jean Opsomer and Sarah Nusser have been awarded a three-year, $280,416 grant from the National Science Foundation (NSF) to come up with a way to account for people missing in population surveys. The U.S. Census Bureau has taken an interest in the research project and will provide funding to support a graduate summer internship.
  
  The researchers plan to use a combination of statistical methods to come up with a new and efficient way to count populations of people.
  
  Through the NSF and Census Bureau funding, a statistics graduate student will spend most of the summer at the Census Bureau in Washington, D.C., analyzing past census records.
  
  "The graduate student will play with the data while we get the theory in order here," Chen says, "and will go to Washington and apply the methodology to the data there so that it will hopefully produce more reliable estimates for the Census Bureau."
  
  Having good population data is important for any number of entities Chen says.
  
  "If we can get a good handle on population surveys and improve the accuracy of the population size it will be a benefit to many," he said.
  
  Politically it's important because Congressional redistricting is based on Census data conducted every ten years. If a state has a mobile or large minority population that is undercounted, they may lose additional Congressional seats.
  
  Much of the federal aid given to states and cities is based upon population size.
  
  Businesses also rely on population surveys.
  
  "Population figures form the base-line for the marketing efforts of U.S. companies," Chen said.
  
  Once the Iowa State statisticians develop a new technique for the population surveys, the method will be useful to more than just the U.S. Census.
  
  "There are no boundaries with this approach. The research can be readily applied to the other surveys," Chen said. "The research will provide understanding and techniques even for wildlife population size estimation."
  
  Chen's interest in population surveys developed when he worked for government research agencies in Australia. There he helped conduct population surveys of tuna.
  
  The new method can be used in the U.S. for any number of wildlife surveys including deer.
  
  "Statistically this is a very challenging problem that will have many uses," Chen said

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February 20 to March 5, 2006

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