for the Consumer Price Index and to provide data for analysis of expenditures in relation to demographic and other characteristics. (For information on the CEX, see Bureau of Labor Statistics, no date; Jacobs and Shipp, 1990.)

Design and Use

The Interview Survey includes a sample of 6,800 consumer units (of which about 5,000 are used for quarterly estimates), interviewed in person at 3-month intervals. Households are in the sample for five quarters (the first interview has a 1-month recall and is used for bounding purposes and to collect an inventory of durable goods). There are monthly rotation groups: each month, one-fifth of the sample is new and one-fifth is completing its fifth and final interview. Household response rates to the Interview Survey have averaged about 85 percent since 1980. There appears to be little time-in-sample bias in the survey, but considerable recall error: for example, apparel expenditures reported for the first month prior to the interview are 124 percent of the monthly mean, while those reported for the third month prior to the interview are only 76 percent of the mean (Silberstein, 1989).

The Diary Survey includes a sample of 6,000 consumer units, each of which records daily expenditures for 2 weeks. Interviews are spread out over the year. Interviewers make three visits to each unit: an initial visit to drop off the first-week diary, a second visit to drop off the second-week diary and pick up the first-week diary, and a third visit to pick up the second-week diary. Household response rates to the Diary Survey have ranged from about 85 to 90 percent.

The CEX covers the U.S. civilian noninstitutionalized population, including military in civilian housing, students in university or college housing, and group homes. (The 1982-1983 interviews excluded the rural population because of budget cuts.) The reporting unit is the consumer unit, defined as one of the following: a single person living alone or sharing a household with others but financially independent; family (household members related by blood, marriage, or adoption); two or more persons living together who share responsibility for two of three major expenses—food, housing, and other expenses. The respondent is any member of the consumer unit aged 16 or older with most knowledge of the unit's finances. People who leave a sampled address are not followed.

In its publications, BLS makes use of data from both the Interview and the Diary Surveys to develop a total picture of expenditures. Comparisons with data from the National Income and Product Accounts (NIPA) indicate that the CEX estimates for some categories are quite complete; these include rent, utilities, fuels, and public services; vehicle purchases; and gasoline and motor oil. But for other categories the CEX estimates fall considerably short: for example, from information provided by BLS, the ratios of CEX to NIPA



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