Box 4.2
Imputation Types for Basic (Complete-Count) Characteristics

Following data capture from census questionnaires and the various levels of nonresponse follow-up, the Census Bureau uses editing and imputation procedures to fill in apparent gaps. The level of imputation required depends on the number of household members who are data defined—that is, whose census records have at least two basic data items reported (counting name as an item). In descending order of known information—and ascending order of required imputation—the various types of imputation performed in the census are:

  1. Item imputation. All members of a household are data defined, but some basic items are not reported or are reported inconsistently; these missing values are supplied through “hot-deck” imputation (termed allocation by the Census Bureau), or through procedures called assignments or edits. Broadly speaking, edit and assignment procedures make use of other information provided by the person; imputation procedures make use of information from other household members or a similar individual in a similar, nearby household.

  2. Whole-person imputation. At least one member of a household is data defined as in (A), but not all members are so defined.

  1. Individual person(s) imputed in an enumerated household. For the members of the household who are not data defined, all basic information is imputed or assigned, item-by-item, on the basis of information about the other household members. An example in 2000 would be a household of seven members that had data reported for six members, and the telephone follow-up failed to obtain information for the seventh person on the household roster (the mail questionnaire allowed room to report characteristics for only six members instead of seven as in 1990). This type 1 imputation is called whole-person allocation by the Census Bureau.

  1. Whole-household imputation There is no data-defined person at the address. Imputation is performed using information from a similar, nearby household or address. Collectively, types 2–5 below are termed whole-household substitution by the Census Bureau.

  1. Persons imputed in a household for which the number of residents is known (perhaps from a neighbor or landlord), but no characteristics are available for them.

  2. Persons imputed in a housing unit known to be occupied for which there is no information on household size.

  3. Persons imputed in a housing unit for which occupancy status and household size have to be imputed first (from among housing units for which occupancy or vacancy status is not known).

  4. Persons imputed in a housing unit for which housing unit status and occupancy status have to be imputed first (from among addresses for which not even status as a housing unit is known).

Types 3–5 were the focus of legal action by the state of Utah. In June 2002, the U.S. Supreme Court declined to characterize such imputation as “sampling,” and hence permitted its use to contribute to state population counts for congressional reapportionment (see Box 2.2).

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