Current Population Survey Design and Methodology - Census Bureau

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metropolitan or micropolitan areas and include at least one county. Micropolitan areas and areas outside of CBSAs are considered nonmetropolitan areas. If any metropolitan area crosses state boundaries, each state-metropolitan area intersection is a separate PSU. 3 3. For most states, PSUs are either one county or two or more contiguous counties. In some states, county equivalents are used: cities, independent of any county organization, in Maryland, Missouri, Nevada, and Virginia; parishes in Louisiana; and boroughs and census divisions in Alaska. 4. The area of the PSU should not exceed 3,000 square miles except in cases where a single county exceeds the maximum area. 5. The population of the PSU is at least 7,500 except where this would require exceeding the maximum area specified in number 4. 6. In addition to meeting the limitation on total area, PSUs are formed to limit extreme length in any direction and to avoid natural barriers within the PSU. The PSU definitions are revised each time the CPS sample design is revised. Revised PSU definitions reflect changes in metropolitan area definitions and an attempt to have PSU definitions consistent with other U.S. Census Bureau demographic surveys. The following are steps for combining counties, county equivalents, and independent cities into PSUs for the 2000 design: 1. The 1990 PSUs are evaluated by incorporating into the PSU definitions those counties comprising metropolitan areas that are new or have been redefined. 2. Any single county is classified as a separate PSU, regardless of its 2000 population, if it exceeds the maximum area limitation deemed practical for interviewer travel. 3. Other counties within the same state are examined to determine whether they might advantageously be combined with contiguous counties without violating the population and area limitations. 4. Contiguous counties with natural geographic barriers between them are placed in separate PSUs to reduce the cost of travel within PSUs. These steps created 2,025 PSUs in the United States from which to draw the sample for the CPS when it was redesigned after the 2000 decennial census. 3 Final metropolitan area definitions were not available from the Office of Management and Budget when PSUs were defined. Fringe counties having a good chance of being in final CBSA definitions are separate PSUs. Most projected CBSA definitions are the same as final CBSA definitions (Executive Office of the President, 2003). Current Population Survey TP66 U.S. Bureau of Labor Statistics and U.S. Census Bureau Stratification of Primary Sampling Units The CPS sample design calls for combining PSUs into strata within each state and selecting one PSU from each stratum. For this type of sample design, sampling theory and cost considerations suggest forming strata with approximately equal population sizes. When the design is self-weighting (same sampling fraction in all strata) and one field representative is assigned to each sample PSU, equal stratum sizes have the advantage of providing equal field representative workloads (at least during the early years of each decade, before population growth and migration significantly affect the PSU population sizes). The objective of the stratification, therefore, is to group PSUs with similar characteristics into strata having approximately equal populations in 2000. Sampling theory and costs dictate that highly populated PSUs should be selected for sample with certainty. The rationale is that some PSUs exceed or come close to the population size needed for equalizing stratum sizes. These PSUs are designated as self-representing (SR); that is, each of the SR PSUs is treated as a separate stratum and is included in the sample. The following describes the steps for stratifying PSUs for the 2000 redesign: 1. A PSU which consists of at least one county that is likely to be part of the 151 most populous metropolitan areas based on projected definitions and Census 2000 population is required to be SR. 2. The remaining PSUs are grouped into non-selfrepresenting (NSR) strata within state boundaries. In each NSR stratum, one PSU will be selected to represent all of the PSUs in the stratum. They are formed by adhering to the following criteria: a. Roughly equal-sized NSR strata are formed within a state. b. NSR strata are formed so as to yield reasonable field representative workloads in an NSR PSU of roughly 35 to 55 housing units. The number of NSR strata in a state is a function of the 2000 population, civilian labor force, state CV, and between-PSU variance4 on the unemployment level. (Workloads in NSR PSUs are constrained because one field representative must canvass the entire PSU. No such constraints are placed on SR PSUs.) In Alaska, the strata are also a function of expected interview cost. c. NSR strata are formed with PSUs homogeneous with respect to labor force and other social and economic characteristics that are highly correlated with unemployment. This helps to minimize the between-PSU variance. 4 Between-PSU variance is the component of total variance arising from selecting a sample of PSUs from all possible PSUs. Design of the Current Population Survey Sample 3–3
d. Stratification is performed independently of previous CPS sample designs. Key variables used for stratification are: • Number of males unemployed. • Number of females unemployed. • Number of families with female head of household. • Ratio of occupied housing units with three or more people, of all ages, to total occupied housing units. In addition to these, a number of other variables, such as industry and wage variables obtained from the Bureau of Labor Statistics, are used for some states. The number of stratification variables in a state ranges from 3 to 7. e. In states with SCHIP sample, the self-representing PSUs are the same for both CPS and SCHIP. In most states, the same non-self-representing sample PSUs are in sample for both surveys. However, to improve the reliability of the SCHIP estimates in Maine, Maryland, and Nevada, the SCHIP non- self-representing PSUs are selected independent of the CPS sample PSUs, with replacement. The methodology for the stratification of PSUs for SCHIP in these states is similar to the other stratifications, except that the stratification variable used is the number of people under age 18 with a household income below 200 percent of poverty. Table 3−1 summarizes the percentage of the targeted population in SR and sampled NSR areas by state. Several current surveys, including CPS, use the Stratification Search Program (SSP) created by the Demographic Statistical Methods Division of the Census Bureau to perform the PSU stratification. CPS strata in all states except Alaska are formed by the SSP. (A separate program performs the stratification for Alaska.) The SSP classifies certain PSUs as SR, using the criteria mentioned previously, and creates NSR strata. First, initial parameter sets for each stratification area (i.e., state or substate area) are formed by creating unique combinations of the number of NSR PSUs, the number of SR PSUs, the number of strata that must be formed, and the average monthly workload for NSR PSUs and SR PSUs. Non-self-representing PSUs are reclassified as SR if additional SR PSUs are needed to provide adequate samples and if they are among the most populous PSUs in the stratification area. Some NSR PSUs are reclassified SR if they are not similar enough to other NSR PSUs to produce a favorable stratification. Some of the created parameter sets are eliminated because of unsatisfactory PSU workloads or lack of a self-weighting design. Next, random stratifications for each parameter set are formed. NSR PSUs are moved from one stratum to another to even out the size of the strata. Stratifications are evaluated based on the criteria in the previous section. A national stratification is then chosen by selecting one stratification from each state. The national stratification is refined through a series of moves and swaps to minimize the difference in workloads among NSR PSUs and the CV for unemployment level for each stratification area. After the strata are defined, some state sample sizes are increased to bring the national CV for unemployment level down to 1.9 percent assuming a 6 percent unemployment rate. A consequence of the above stratification criteria is that states that are geographically small, mostly urban, or demographically homogeneous are entirely SR. These states are Connecticut, Delaware, Hawaii, Massachusetts, New Hampshire, New Jersey, Rhode Island, Vermont, and the District of Columbia. Selection of Sample Primary Sampling Units Each SR PSU is in the sample by definition. There are currently 446 SR PSUs. In each of the remaining 378 NSR strata, one PSU is selected for the sample following the guidelines described next. Four of the NSR strata only contain SCHIP sample. At each sample redesign of the CPS, it is important to minimize the cost of introducing a new set of PSUs. Substantial investment has been made in hiring and training field representatives in the existing sample PSUs. For each PSU dropped from the sample and replaced by another in the new sample, the expense of hiring and training a new field representative must be accepted. Furthermore, there is a temporary loss in accuracy of the results produced by new and relatively inexperienced field representatives. Concern for these factors is reflected in the procedure used for selecting PSUs. Objectives of the selection procedure. The selection of the sample of NSR PSUs is carried out within the strata using the Census 2000 population. The selection procedure accomplishes the following objectives: 1. Select one sample PSU from each stratum with probability proportional to the 2000 population. 2. Retain in the new sample the maximum number of sample PSUs from the 1990 design sample. Using a procedure designed to maximize overlap, one PSU is selected per stratum with probability proportional to its 2000 population. This procedure uses mathematical programming techniques to maximize the probability of selecting PSUs that are already in sample while maintaining the correct overall probabilities of selection. 3–4 Design of the Current Population Survey Sample Current Population Survey TP66 U.S. Bureau of Labor Statistics and U.S. Census Bureau
Page 1 and 2: Design and Methodology Current Popu
Page 3 and 4: U.S. Department of Labor Elaine L.
Page 5 and 6: Foreword The Current Population Sur
Page 7 and 8: CONTENTS Chapter 9. Data Preparatio
Page 9 and 10: CONTENTS Figures 3-1 CPS Rotation C
Page 11 and 12: Chapter 1. Background The Current P
Page 13 and 14: Chapter 2. History of the Current P
Page 15 and 16: in small circles with an ordinary l
Page 17 and 18: was added as a control to the Hispa
Page 19 and 20: More detailed information on these
Page 21: social and economic characteristics
Page 25 and 26: Calculation of overall state sampli
Page 27 and 28: use of census information to reduce
Page 29 and 30: Summary of Sampling Frames Table 3-
Page 31 and 32: Examples of Post-Sampling Code Assi
Page 33 and 34: 2. The sample for 1 month is compos
Page 35 and 36: Chapter 4. Preparation of the Sampl
Page 37 and 38: Even without geographic clustering,
Page 39 and 40: Permit listing. Listing in the perm
Page 41 and 42: Chapter 5. Questionnaire Concepts a
Page 43 and 44: Employed citizens of foreign countr
Page 45 and 46: ‘‘What are all of the things yo
Page 47 and 48: Chapter 6. Design of the Current Po
Page 49 and 50: Item Response Analysis The primary
Page 51 and 52: Industry and occupation—Dependent
Page 53 and 54: months. For people reported to be l
Page 55 and 56: Oksenberg, L., C. Cannell, and G. K
Page 57 and 58: Figure 7−1. Introductory Letter 7
Page 59 and 60: Figure 7-3. Noninterviews: Main Ite
Page 61 and 62: Figure 7-5. Summary Table for Deter
Page 63 and 64: eason, the CATI facilities generall
Page 65 and 66: Figure 7-9. Interviewing Results (S
Page 67 and 68: transmitted directly to the compute
Page 69 and 70: Chapter 9. Data Preparation INTRODU
Page 71 and 72: Demographic-related recodes are cre
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sample unit (person or household) b
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still be associated with the state-
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Weights After National Coverage Adj
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Table 10−4: Second-Stage Adjustme
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Iteration 2: (Repeat steps above be
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1. For each state 7 and the Distric
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Production of monthly, quarterly, a
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for national CPS labor force series
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Chapter 11. Current Population Surv
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Table 11-1. Current Population Surv
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have completed their eighth and fin
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Table 11−3. Summary of 2004 ASEC
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Current Population Survey TP66 U.S.
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Chapter 12. Data Products From the
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Table 12-1. Bureau of Labor Statist
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Chapter 13. Overview of Data Qualit
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For example, we now recognize that
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the other panel in the SR SECU or N
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means that the estimates of varianc
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Table 14-2. Components of Variance
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Table 14-4. Effect of Compositing o
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Wolter, K. (1984), ‘‘An Investi
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• Master Address File (MAF): The
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no RO review of group quarters list
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5. The questionnaire does not elici
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chance to answer; probing technique
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Chapter 16. Quality Indicators of N
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Figure 16−2. Average Yearly Type
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Table 16-3. Labor Force Status by I
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supposed to be done in person, the
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Figure 16−4. Basic CPS Household
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Appendix A Sample Preparation Mater
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Illustration 1. Segment Folder, BC-
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Illustration 3. Unit/Permit Listing
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Illustration 5. Unit/Permit Listing
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Illustration 7. Permit Sketch Map,
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group numbers are chosen for deleti
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demographic components often cited
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2. The CPS control universe exclude
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A concern exists relative to the co
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The resulting race categories (Whit
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treat race and Hispanic origin as a
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REFERENCES Ahmed, B. and J. G. Robi
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Figure D-1. Map D-2 Organization an
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This report provides the supervisor
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Appendix E. Reinterview: Design and
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Acronyms ADS Annual Demographic Sup
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Births—Con. total population C-4
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Estimates, population—Con. popula
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Listing checks 15-4 Listing Sheets
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Ratio adjustments—Con. second-sta
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Vacancy rates 11-2, 11-4 Variance e
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