Changes

"Hot deck" imputation is a way to solve the problem that people do not return their census questionnaires. The hot-deck imputation technique replaces blanks with an estimate based on the actual response made by similar people.<ref> See John Stiller and Donald R. Dalzell, "Hot-deck Imputation with SAS Arrays and Macros for Large Surveys," (1997) [http://www2.sas.com/proceedings/sugi23/Stats/p246.pdf online]</ref> The Census has always used imputation--for example, by asking one person to describe everyone else in the building and not actually talking to the other people. The Hot Deck adjustment technique has been explicitly approved by the Supreme Court<ref> Utah v. Evans, 536 U.S. 452 (2002)[http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=CASE&court=US&vol=536&page=452 online]</ref> even though it can have an effect on the enumeration used to apportion the House. The Supreme Court has ruled it is not sampling, but a way to reduce errors in actual enumerations.

"Hot deck" imputation is a way to solve the problem that people do not return their census questionnaires. The hot-deck imputation technique replaces blanks with an estimate based on the actual response made by similar people.<ref> See John Stiller and Donald R. Dalzell, "Hot-deck Imputation with SAS Arrays and Macros for Large Surveys," (1997) [http://www2.sas.com/proceedings/sugi23/Stats/p246.pdf online]</ref> The Census has always used imputation--for example, by asking one person to describe everyone else in the building and not actually talking to the other people. The Hot Deck adjustment technique has been explicitly approved by the Supreme Court<ref> Utah v. Evans, 536 U.S. 452 (2002)[http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=CASE&court=US&vol=536&page=452 online]</ref> even though it can have an effect on the enumeration used to apportion the House. The Supreme Court has ruled it is not sampling, but a way to reduce errors in actual enumerations.

==Undercount and Overcount==

==Undercount==

Statisticians now estimate that the 1990 Census missed about 4.7 million people who should have been counted.  They estimate that the 2000 Census missed 6.4 million people, and double counted 3.1 million others, for a net undercount of 3.3 million. For example, only 64% of the people return the mailed forms.  To reach the other 36% the Census tries multiple followup visits in person. These are very expensive, and even then many people refuse to answer the door. It costs $100 million dollars to reach another 1% of the missing 36%. People who moved around are sometimes counted twice, as are some students and prisoners who can be counted at home and at their institutions. Children of divorced parents are often listed by both parents. Some households are so complicated or chaotic that the person filling out the forms is unclear who is living there today.<ref> See Freedman and Wachter (2004) pp. 6-8</ref>

Statisticians now estimate that the 1990 Census missed about 4.7 million people who should have been counted.  They estimate that the 2000 Census missed 6.4 million people, and double counted 3.1 million others, for a net undercount of 3.3 million. For example, only 64% of the people return the mailed forms, representing 200 million people.  To reach the other 36%--100 million or so-- the Census tries multiple followup visits in person, or asks the neighbors. Even then many people refuse to answer the door. Many people do not want the government knowing there whereabouts, even and ignore Census promises that it will not reveal that information to any other government agency. It will cost $30,000 dollars to reach another 1000 of the missing 36%, or about $3 billion to reach all 100 million of them.

People who moved around are sometimes counted twice, as are some students and prisoners who can be counted at home and at their institutions. Children of divorced parents are often listed by both parents. Some households are so complicated or chaotic that the person filling out the forms is unclear who is living there today.<ref> See Freedman and Wachter (2004) pp. 6-8</ref>

==Further reading==

==Further reading==