Assessing Asset Data on Low-Income Households - Urban Institute

of the list sample, which oversamples wealthy families. Wealthy families are less likely to
respond in any survey, but the SCF includes a means of identifying the level of nonresponse
among wealth groups. The response rate for the area-probability sample was 68.1 percent,
however, while the response rate for the list sample (wealthy household oversample) was 30.1
percent. Members of the list sample, unlike the area-probability sample, were given the
opportunity to opt out of being interviewed before an SCF interviewer first approached them by
returning a postcard to refuse participation. This mode of nonresponse explains less than a fifth
of all nonresponse for the list sample in 2001 (Kennickell 2005). However, SCF respondents
provide answers to asset and liability questions more often than SIPP respondents. Czajka et al.
(2003) finds that imputation rates in the 1998 SCF were one-half to two-thirds the imputation
rate for associated variables in the 1996 SIPP (p. 90).
To impute missing values, the SCF uses a complicated model-based procedure, which is
different from the procedure used for the SIPP and PSID. For nearly every variable, missing
values are imputed five times, and these five values are stored in the final SCF data sets. These
five imputed values are obtained by drawing repeatedly from an estimate of the conditional
distribution of the data. Because families have five values for each answered question, the data
may initially be more difficult for the novice user to use. But these multiple imputations have
distinct advantages. They allow for more statistically efficient estimates. In addition, they make
it possible to quantify the amount of uncertainty introduced by missing data, thus enabling more
honest calculations of statistical significance.
As with the SIPP and PSID, if respondents are unable to provide the exact value of an
item, they are given the option of choosing a range from a pre-selected set of ranges or providing
a range in which the value of an item falls. This range is then incorporated into the imputation
for that item.
The Federal Reserve goes to great lengths to ensure that they are providing the general
public with high quality data. The Computer Assisted Personal Interview (CAPI) instrument
employed by SCF interviewers uses extremely careful wording and logic checks. Interviewers
also record their comments about the interview and any responses that might require
clarification. Interviewers are also required to complete a debriefing questionnaire after each
interview. When the data arrive at the Federal Reserve, they are extensively checked using
automated computer programs and, using interviewer notes, are edited to resolve inconsistencies
when possible (Athey and Kennickell 2005). Because the main objective of the SCF is to obtain
accurate information on assets, liabilities, and net worth in the United States, evaluations of other
data sets’ asset and liability information is often based on comparisons to the SCF.
Survey Administration. The SCF uses both face-to-face and telephone interviews, both
of which are conducted using Computer-Assisted Interviewing. An attempt is made to reach
every sample case in person to make an initial effort to gain cooperation for the interview, but
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