BOX 3-2 Classification of Primary Sampling Units (PSUs)

The 91 PSUs used in the CE sample are classified into four categories:

  1. 21 “A” PSUs, which are metropolitan core-based statistical areas (CBSAs) with a population over 2 million people
  2. 38 “X” PSUs, which are metropolitan CBSAs with a population under 2 million people
  3. 16 “Y” PSUs, which are “micropolitan” CBSAs, defined as areas that have at least one urban cluster of at least 10,000 but less than 50,000 population, plus adjacent territory that has a high degree of social and economic integration with the core as measured by commuting ties
  4. 16 “Z” PSUs, which are non-CBSA areas, and are often referred to as “rural” PSUs

SOURCE: Bureau of Labor Statistics (2012, p. 5).

Implementation of the Interview Survey

Figure 3-1 displays the flow process of the Interview survey. Work on the Interview survey begins each month with one-third of the quarterly sample. The Interview survey had an overall response rate of 73 percent in 2010. (See “Comparison of Response Rates” in Chapter 5, for a discussion of how these rates are calculated.) Households receive a pre-survey notification letter. The Interview survey is designed for collection through an “in-person” visit by a field representative, and most data are collected in this fashion. However, field representatives are allowed to fall back to a telephone interview and often do. Of completed cases in 2010,1 approximately 17 percent were completed entirely via the telephone, and an additional 48 percent were completed in part over the telephone. The relative number of cases completed over the telephone increases over later phases of the survey. Of interviews completed in quarter 1 (initial interview), only 2 percent were interviewed entirely via telephone and an additional 34 percent had some data collection over the phone. By quarter 5 in the rotation, 22 percent of completed interviews were conducted entirely over the telephone, and an additional 50 percent had some data collected over the phone. Whether via personal visit or over the telephone, the field representative uses a computer-assisted personal interviewing (CAPI) instrument.


1Data on interviews by mode for 2010 come from an internal spreadsheet of costs provided to the panel by BLS.

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