The Bureau of Labor Statistics (BLS) obtains Consumer Expenditure Surveys (CE) Interview Survey and Diary Survey data by interviewing respondents about their expenditures, income, and characteristics. The U.S. Census Bureau selects the samples of household addresses and collects the data under contract with BLS.
A selected sample household address is mailed an advance letter from the Census Bureau informing the residents about the purpose of the survey and the upcoming visit by the interviewer. The Census Bureau conducts both the Interview Survey and the Diary Survey primarily by personal visit with some telephone interviewing. The interviewer uses a structured questionnaire to collect the demographic and income data in the Interview and Diary Surveys. The structured questionnaire is also used to collect expenditure data in the Interview Survey. Expenditure data in the Diary Survey are entered by the respondent into a paper or online diary form. Any eligible household member who is at least 16 years old can serve as the respondent in either survey.
The Interview Survey collects detailed data on types of expenditures that are usually fairly easy to recall for periods of 3 months or longer. On average, it takes 67 minutes to complete the interview.
Each consumer unit (CU) at a sampled Interview Survey address remains in the sample for four quarters and is interviewed every 3 months. The sample of addresses for each quarter is divided evenly across three monthly panels and each address remains in the same monthly panel each quarter. For example, if an address is first included in the sample in the second month of a calendar quarter (e.g., February), then it will be in the sample in the second month of the following three quarters (e.g., May, August, November). Because the sample is based on address, the CU that is interviewed at the address may be interviewed up to four times. However, if the CU moves from the sampled address, that CU will no longer be interviewed. Any new CU moving into the address will be interviewed instead for whatever time remains for that address in sample.
After the fourth interview, the address is dropped from the survey and replaced by a new address. For the survey as a whole, 25 percent of the sample in each quarter consists of new addresses introduced into the sample to replace the addresses that have been in the sample for four quarters. Data collected in each quarter are treated independently, so that published 12-month estimates are not dependent upon a particular family participating in the survey for a full four quarters.
Exhibit 1 shows how Interview Survey addresses rotate in and out of the sample. In this example, the first interviews start in April, May, and June 2021. Three months later, the second interviews begin. A CU at a sample address first interviewed in April 2021 is re-interviewed in July 2021, October 2021, and January 2021. And while the second set of interviews begins in July 2021 for the units first interviewed in April, a new set of addresses is starting their set of four interviews.
|Interview year and month||Interview set|
Note: The column headings are the interview numbers. Each letter designates a panel or group of household addresses. Each panel consists of interviews conducted every three months for four quarters.
Source: Bureau of Labor Statistics.
During the first interview (interview set 1 in exhibit 1) information is collected on demographic and family characteristics and on the inventory of major durable goods for each CU. This socioeconomic information is used by BLS to classify the CU for the publication of statistical tables and economic analyses. Also collected in the first and fourth interviews are wage, salary, employment, and income (including unemployment compensation; income from royalties, dividends, and estates; and alimony and child support) information of each member of a CU who is age 14 years or older.
Expenditure data are collected in each interview via multiple question patterns depending on the types of expenditures collected. One question pattern asks the respondent for the month of purchase of each reported expenditure. A second question pattern asks for quarterly amounts of expenditures. A third question pattern asks for the payment frequency and the amount based on said frequency. In the fourth interview, an annual supplement collects information on financial assets and liabilities (debts).
The Diary Survey is a separate survey designed to collect smaller, more frequently purchased items. Two separate instruments are used by the Census Bureau to collect Diary Survey data: a household characteristics questionnaire and a record of daily expenses (also known as the “diary”). In the household characteristics questionnaire, the interviewer records information pertaining to age, sex, race, marital status, and family composition, as well as information on the work experience and earnings of each member of the CU. Like the Interview Survey, BLS uses this socioeconomic information to classify the CU for publication of statistical tables, as well as for economic analyses.
The record of daily expenses is designed as a self-reporting diary, in which respondents record a detailed description of all expenses made by all CU members for two consecutive 1-week periods. Diary keeping begins on the day following the completion of the household characteristics questionnaire. Data collected each week are treated as statistically independent for publications—each week’s diary is separately weighted to be representative of the sample. The diary is divided by day of purchase and by four classifications of goods and services—meals, snacks, and drinks away from home; food and drinks for home consumption; clothing, shoes, jewelry, and accessories; and all other products, services, and expenses. The items reported are subsequently coded by the Census Bureau so that BLS can aggregate individual purchases for representation in the CPI and for presentation in statistical tables.
The Diary Survey asks for almost all expenses that the CU incurs during the survey week. Expenses incurred by CU members while away from home overnight or longer are not in scope for the diary and are excluded. It takes approximately 20 minutes over two visits for the interviewer to collect the demographic data and to instruct the respondent on how to keep the diary. It is estimated that it takes the respondent 10 minutes each day to enter expenses into the diary.
Data collection quality control and data integrity are provided by a re-interview program, which evaluates the performance of the individual interviewer, to determine how well the procedures are being carried out in the field. The re-interview is conducted by a Census Bureau supervisor or an interviewer at a national processing center data contact center (a centralized telephone call center for conducting interviews). Subsamples of approximately 9 percent of households in both the Interview and Diary Surveys are re-interviewed on an ongoing basis.
All data collected in both surveys are subject to Census Bureau and BLS confidentiality requirements that prevent the disclosure of the respondents' identities. The information that respondents provide is used solely for statistical purposes. All Census Bureau and BLS employees who work with the CE data take an oath of confidentiality and are subject to fines and imprisonment for improperly disclosing information provided by respondents. Confidentiality certification training is required annually.
Names and addresses are removed from all forms and datasets prior to transmission from the Census Bureau to BLS and are not included in any statistical releases. At BLS, the data are processed and stored on secure servers, with access limited to employees having the appropriate security clearances. As a further precaution, BLS applies certain restrictions to the microdata available on the public-use files. These include geographical and value restrictions that prevent the identification of respondents.
The Census Bureau, under contract with BLS, carries out data collection for both the Interview Survey and the Diary Survey. In addition to its collection duties, the Census Bureau does field editing and coding, checks consistency, ensures quality control, and securely transmits the data to BLS. In preparing the data for analysis and publication, BLS performs additional review and editing procedures.
The first step of quality control in the Interview Survey is in the computer assisted personal interview (CAPI) instrument that Census Bureau interviewers have used to collect interview survey data since April 2003. The CAPI instrument enforces question skip patterns and prompts the interviewer to confirm unusually low or high expenditure values. For some expenditures, the CAPI instrument also provides a list of expenses reported in previous interviews to prevent duplication of reports.
At the completion of the interview, data are electronically transferred from an interviewer’s laptop to the Census Bureau’s master control system. The Census Bureau conducts post-processing by reformatting the data into datasets based on the required BLS output structure and performing special processing, including converting missing values to special characters and removing any personally identifiable information. Some “inventory” data that are not expected to change, such as vehicle and mortgage information, are copied into an input file that is loaded onto the laptops for subsequent interviews during the next quarter. This way, a few questions related to those expenditures are updated each quarter, rather than an entire data record. Names and addresses of respondents are not transmitted to BLS.
At the beginning of the 2-week collection period, the Census Bureau interviewer, using the household characteristics questionnaire (a CAPI instrument), records demographic information on members of each sampled CU. In some cases, interviewers will also ask respondents at this time about work experience and income. Upon completion of the household characteristics questionnaire, the interviewer provides the respondent with two 1-week diaries and instructs them how to fill it out. During the diary-keeping period, the interviewer periodically checks in with the CU to answer any questions. At the end of the diary keeping period, the interviewer collects the diary, reviews the entries, and works with the CU to add any expenses that may have been missed. During this time, the interviewer will ask questions about work experience and income, if they have not already done so.
Data from the household characteristics questionnaire are reviewed for completeness and consistency and then are scanned and transcribed into a database. Expenditure descriptions written by the respondent are assigned to different codes by staff with the assistance of a computer program developed to assign codes for commonly used descriptions. The final data are transmitted to Census Bureau’s headquarters, along with any scanned image files of the diaries. Census Bureau staff combines expenditure data from diaries with data collected in the household characteristics questionnaire, removes personal identifiable information, and transmits the merged files to BLS on a monthly basis.
BLS periodically provides new requirements to the Census Bureau for updating the Interview Survey questionnaire and the Diary Survey form to incorporate new products and services, clarify instructions, improve instrument navigation, incorporate changes requested by stakeholders, and streamline the interview by deleting outdated items. Although major changes to the questionnaire are made every other year, BLS staff who work on the CE continuously monitor the emergence of new goods and services available in the marketplace, as well as changes in the relative importance of existing items in consumers’ budgets. Updated information on how to report new goods and services is provided to the interviewers on a regular basis.