When census-takers can’t reach anyone at a particular address or obtain information about occupants in other ways, they sometimes use a last-resort statistical technique called “imputation” to fill in missing data. One marker of the quality of a census is how much it relies on imputation to add people to the count. http://pewresearch.org/pubs/1981/census-imputation-missing-housing-units-people-number-type  [Using Made Up Numbers] Census Update: What the World Will Look like in 2050Read more: http://www.time.com/time/nation/article/0,8599,2080404,00.html

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