in person because of the use of continuation forms (see Section 3-B.2). However, in list/enumerate areas, because of a data processing error, the continuation forms for large households were lost, and the imputation process may not have imputed all of the people on the lost forms back into the census (Rosenthal, 2003b:6).

The numbers of people requiring imputation in households for which only occupancy status and household size were reported (type 2) were roughly similar in all three censuses. The larger number of wholly imputed people in households of types 3–5 (for which, at a minimum, household size had to be imputed) in 2000 compared with 1990 and even 1980 is difficult to explain, although processing errors may have contributed to this outcome (see end of this section). Information is not available with which to evaluate the reasonableness of the numbers of type 4 and 5 whole-household imputations as percentages of the numbers of addresses for which imputations could have been possible; that is, the Census Bureau has not provided the denominators with which to calculate imputation rates for these two categories.

Whole-person and whole-household imputations varied by geographic area. In particular, the small number of people imputed in 2000 when it was not even clear whether the address was a housing unit (type 5) were concentrated in rural list/enumerate areas (e.g., the Adirondacks region of New York State, rural New Mexico).13 In these areas, enumerators developed an address list and enumerated the units at the same time. Although there was a follow-up operation to recheck the status of units that the enumerators classified as vacant (Hough and Borsa, 2003:21), the status of some units was apparently not resolved.

A question is how many of the imputed people in households for which a household size had to be imputed (types 3–5) represented correct enumerations—some of them may have been erroneous in thatthehouseholddidnotcontainasmanypeopleaswereimputed into it. Alternatively, not enough people may have been imputed into some households. A related question is whether the basic characteristics assigned to imputed people in all of the imputation types accurately reflected the true distributions.


From analysis by panel staff of U.S. Census Bureau, Census Tract Imputation File, provided to the panel April 4, 2002.

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