Consumer Expenditure Survey Anthology, 2008 41

Reclassifying LowExpenditure Consumer

Units in the Consumer

Expenditure Interview

Survey

Steven Bass One of the primary uses of data

from the Consumer Expenditure Survey (CE) is the computation of weights representing the

purchases of goods and services in the

construction of the Consumer Price

Index (CPI), a principal Federal economic indicator. Accurate representation of actual expenditures is thus critically important beyond usual data quality standards. The CE processing system has several screening processes

in place to ensure data quality. One

such process is the minimal expenditure edit, which screens out consumer

units (CUs)1 with unusually low reported total expenditures for further

investigation, to determine whether

they should be reclassified as noninterviews—that is, whether they should be

treated as if they had refused to take

part in the survey. Data from noninterviews are not used in the computation

of official expenditure estimates from

the CE. A minimal expenditure edit has

been implemented for the CE Diary Survey since 2002. In April 2006, a minimal

expenditure edit was implemented for

the CE Interview Survey, to investigate

cases with very low expenditures. This

article describes the methodology of

the minimal expenditure edit for the Interview Survey, as well as the results

attained from its first year of implementation.

Background

Both Interview and Diary Survey data

go through a series of edits before publication. Among these edits are consistency checks, outlier review, imputation,

and weighting. Minimal expenditure

edits for both surveys take place early

in the production process, prior to CU

weighting and any expenditure or income imputation. Although the minimal expenditure edit process for each

survey is essentially the same, a number of differences exist because the

Diary Survey is self-administered while

the Interview Survey is administered

by a field interviewer. For the Diary

Survey, respondents record all their expenditures in a diary for two consecutive 1-week periods. It is difficult to

ensure that a respondent has completed the Diary form accurately, including all of his or her expenditures, because no one is observing the process.

For this reason, the minimal expenditure edit process for the Diary Survey

is much more structured than that for

the Interview Survey.

The Diary minimal expenditure edit

process uses the number of expenditures recorded, the total amount recorded, and CU characteristics (such

as the size of the CU) to determine

whether a low report for total expenditures by a CU is legitimate. As part of

the reclassification algorithm, urban

CUs have to meet a higher expenditure

threshold than rural CUs, because rural CUs are more likely to do their shopSteven Bass is an economist formerly working in the Division of Consumer Expenditure Surveys, U.S. Bureau of Labor Statistics.

1

 See the glossary in Appendix: Description

of the Consumer Expenditure Survey for the

definition of a consumer unit.
42 Consumer Expenditure Survey Anthology, 2008

ping less often. Students and small

CUs also are treated differently because of their lower expected expenditure levels. In 2006, more than 800 of

the nearly 20,000 eligible diaries were

from CUs that were reclassified as

noninterviews. The process is entirely

automated, and none of the individual

CU reclassifications are manually reviewed.

In contrast to the Diary Survey,

which is a self-administered paper survey, the Interview Survey is a computerassisted personal interview (CAPI).

Using a laptop computer, the field interviewer asks the respondent a series

of questions about his or her expenditures and records the responses.2

 To

reduce respondent burden, most sets

of related questions (such as those

having to do with telephone expenses)

are preceded by a screener question

(for example, “Have you received any

bills for telephone services?”). If the

respondent has not received any telephone bills, the entire section can be

skipped by answering “No” to the question. However, although a “No” answer

can help avoid unnecessary followup

questions, respondents may respond

“No” to screener questions (even

though they have applicable expenditures) in order to skip over questions

and minimize the time it takes to complete the interview. The minimal expenditure edit is meant to screen out such

invalid cases of low total expenditures.

The Interview minimal expenditure

edit process was intended to screen for

three separate potential problems:

• CUs effectively refusing to participate in the survey by answering “No” to all or most of the

screener questions or refusing to

answer individual questions.

• Field interviewers fraudulently

completing the survey without

interviewing the CU.

• Field interviewers not asking all

of the questions to certain groups

of people (for example, skipping

questions to students about

owned properties).

Methodology

In the minimal expenditure edit process

for the Interview Survey, CUs are selected by an automated procedure and

are manually reviewed on an individual

basis. Two factors—the length of the

interview and the total sum of expenditures reported—are used to determine

whether a CU should be investigated.

In the computation of total expenditures reported by a CU, “Don’t know”

or “Refused” responses are treated as

zeroes. Although some questions ask

for quarterly values while others ask

for monthly values, these different reference periods are not standardized to

the same period for the purposes of the

minimal expenditure edit.

A CU’s records are manually reviewed in greater detail if

• The total sum of expenditures is

less than $100 or

• The total sum of expenditures is

between $100 and $300, and the

interview time is less than 15 minutes.

In the manual review of the CUs

screened out by the automated process, other variables in addition to total

expenditures and interview time are

used to evaluate a case. These additional variables are related to expenditure reporting characteristics (such as

the number of expenditures recorded

and the number of “Don’t know” or

“Refused” responses), respondent

characteristics (such as the respondent’s

age, the size of the CU, whether the

CU is in an urban or a rural location,

and whether the CU resides in public

housing or student housing), and data

collection characteristics (such as

whether the interview is a telephone

or personal interview and the number

of visits to the CU by the field interviewer). A detailed record of all the

CU’s expenditures and any field interviewer notes are taken into consideration, as is information provided by the

CU in previous interviews.

CUs that are manually reviewed in

the minimal expenditure edit process

are presumptively treated as noninterviews. The review process consists of

a search for mitigating factors that

would explain the low level of expenditures for the quarter. Elderly respondents, college students, recipients of

food stamps, and occupants of public

housing are almost always treated as

valid low expenditure cases, because

they tend to have lower expenditure

levels than the general population has.

If the respondent has a high number

of “Don’t know” or “Refused” responses, that is also taken as evidence

of a proper interview, because such respondents still provide information on

the specific items purchased by a CU.

Expenditure amounts for “Don’t know”

and “Refused” responses are imputed

later. Often, field interviewer notes also

will provide valuable information, such

as expenses that have been paid for

by parents or other relatives. If no persuasive reason can be found to explain

the low level of expenses for the 3-

month recall period, the CU is reclassified as a noninterview and is excluded

from the computation of official estimates from the CE.

Results

The Interview Survey minimal expenditure edit was implemented in 2006. For

that year, 49 CUs were reclassified as

noninterviews, out of a total of 257

flagged by the edit process. These reclassified CUs differed significantly

from the general population of CUs.

(See table 1.) Specifically, reclassified

cases have much lower expenditure

totals, interview time, and reported income than the general population has.

Although data can be collected either

in person or over the phone, in-person

interviews generally elicit higher quality data. Reclassified interviews are

more likely to have taken place over

the phone. Also, respondents are more

likely to have been converted refusals,

a term used for CUs that initially refuse

to participate in the survey. In addition,

2

 The Interview Survey moved from a

paper form to the CAPI format in April

2003. For more information, see L. Groves,

“Computer-Assisted Personal Interviewing

for the Consumer Expenditure Interview

Survey,” Consumer Expenditure Survey

Anthology (Bureau of Labor Statistics,

2003), p. 18.
Consumer Expenditure Survey Anthology, 2008 43

the complete absence of any record usage (for example, credit card statements

or receipts) shows a low level of diligence on the part of respondents in

these CUs.

The differences between the reclassified interviews and those flagged by

the process but not reclassified are enlightening. (See table 1.) Although the

income level is still low, cases that are

flagged but not reclassified have a

much higher income level than the reclassified cases. They also have a

higher rate of personal interviews and

a lower rate of converted refusals. Students and residents of public housing

are also among those who are less likely

to be reclassified.

Although low annual income would

seem to be a reasonable explanation for

low expenditure totals, it is likely to be

unrepresentative of true income in

many cases. The income questions in

the Interview Survey are asked at the

end of the interview and are part of the

Work Experience and Income section.

Many respondents choose not to answer these questions fully. In the Interview Survey minimal expenditure edit

process, annual income is used mostly

as a proxy for respondent diligence.

Beginning with 2004 data, the CE implemented an income imputation process

to correct for the low response rate of

income questions. The Interview Survey minimal expenditure edit is performed at an earlier stage of processing, and only the reported income data

are used in the edit.

In addition to reclassifying CUs to

noninterview status, the April 2006 minimal expenditure edit revealed that a

field interviewer had been systematically falsifying data, and those falsified cases were removed from the database. These cases accounted for 5 of

the 49 reclassified CUs. The expenditure data compiled for that edit also

have been useful as data quality measures in other analyses. The number of

expenditure questions answered, the

number of “Don’t know” or “Refused”

responses to expenditure questions,

and the total reported expenditures before processing are variables that were

created specifically for the Interview

Survey minimal expenditure edit. However, these variables also serve as indicators of data quality and have been

used in other recent research on the

Interview Survey (such as comparing

the quality of reporting between converted refusers and other respondents

and comparing the quality of responses

among different treatment groups in an

incentive experiment). The data compiled by the edit process can be used

to examine other issues as well. CUs

with high expenditure totals and short

interview times could be interpreted as

evidence of inaccurate information provided by the respondent or of fraudulent data entered by the field interviewer.

In addition, the data can be used to

investigate the correlations between

expenditures and other variables, such

as participation in public housing or in

food stamps programs.

Conclusion

Analysis of the effectiveness of the

minimal expenditure edit process in the

Interview Survey is still ongoing. So

far, the low number of reclassified cases

has had a negligible effect on the computation of official expenditure estimates from the CE. Further analysis is

necessary to determine whether the

thresholds used in the edit should be

revised to increase the number of cases

evaluated.

One consideration for future implementations of the Interview minimal expenditure edit is automation. Currently,

cases are selected for manual review

on the basis of a fixed set of criteria,

but the ultimate decision to reclassify

is left to the reviewer. A rule-based approach would increase the consistency

of the edit by removing human error, in

addition to saving the reviewer time,

thereby allowing him or her to consider

a larger number of cases. However, this

change would come at the expense of

flexibility. Experimentation with a more

extensive set of criteria, as well as an

analysis of the tradeoff between false

positives and false negatives, is needed

to determine whether the process

should be modified to achieve the appropriate balance.
44 Consumer Expenditure Survey Anthology, 2008

Table 1. Comparison of average expenditures, income, and characteristics, by type of interview,

Consumer Expenditure Survey, second quarter 2006 to first quarter 2007

Expenditure total .................................................................. $8,542 $44 $42

Necessities total1 ................................................................. $2,325 $18 $19

Total time2 .............................................................................. 60 minutes 29 minutes 32 minutes

Annual income3 .................................................................... $30,405 $45 $440

CU size ................................................................................. 2.4 persons 1.7 persons 1.5 persons

Age of respondent .............................................................. 49 53 53

Other statistics (percent):

Personal interviews4 ............................................................ 67.2 55.1 72.6

Converted refusal5 .............................................................. 11.7 38.8 20.7

Usage of records6 .............................................................. 47.4 0 3.4

Food stamps ........................................................................ 4.7 4.1 4.3

Student housing ................................................................... 1.1 12.2 16.8

Public housing ...................................................................... 2.7 4.1 18.8

Good interviews

(n = 32,554)

Reclassified

cases (n = 49)

Flagged but not

reclassified

 (n = 208)

Item

1

 The necessities total statistic is the sum of the amounts

spent on groceries, utilities, and housing payments—items

for which almost all CUs should report expenditures. 2 Total time is the amount of time spent in the interview

process. 3

 Annual income reported here is lower than published

income for two reasons. First, respondents who are unwilling

to reveal their income levels have the option of selecting an

income bracket instead. An income equal to the median of

reported incomes inside the bracket selected is then imputed.

Second, data are imputed for incomplete income reporters.

Income data reported in this table are compiled prior to both

bracket and income imputation.

4

 The Interview Survey is conducted either in person or

over the phone. In-person interviews are the preferred

method, because they generally elicit higher quality data. 5

 The designation converted refusal is selected at the discretion of the field representative if the respondent initially

refused the survey, but was eventually convinced to participate. 6

 In the survey assessment section, the field interviewer is

asked whether the respondent “Always, almost always, mostly,

occasionally, almost never, or never” used records (such as

receipts or credit card statements) to answer the questions.

The entry “usage of records” is the percentage of CUs classified in a category other than “never.”