Abstract

Shail Butani, Lawrence Cahoon, Robert Fay, and Donna Kostanich. (1994) "Measurement of Different Design Effects," Proceedings of the Section on Survey Research Methods, American Statistical Association, 778-783.

The Current Population Survey (CPS), the monthly labor force survey that the U.S. Bureau of the Census conducts for the U.S. Bureau of Labor Statistics (BLS), uses state probability samples (state-based design) totaling about 60,000 households. In January 1994, CPS interviewers began collecting data in an entirely computer-assisted environment, using a new questionnaire. Before introducing the new data collection method, the Census Bureau and BLS tested it on a separate national probability sample of 12,000 households. The results of this parallel survey (PS), which ran from July 1992 through December 1993, indicated that the CPS annual average unemployment rate would have been 0.45 percentage point higher in 1993 had the new data collection method been used. For a general discussion of the results, see the February 1994 Employment and Earnings (Bureau of Labor Statistics, 1994, Vol. 41, No. 2); for a more detailed discussion, see Polivka (1994).

The above difference of 0.45, however, provides an estimate of only the overall effect on a 1993 annual average basis. In this paper, we discuss the measurement of design differences between the PS and the CPS in January 1994 and subsequent months to better understand the transition effects that were not accounted for. We concentrate our analysis on the effects of: 1) differences in the proportion of households interviewed from centralized facilities; 2) use of 1990-based population controls, adjusted for census undercount, rather than 1980-based controls formerly used; 3) differences in ratio adjustment methods; 4) use of composite estimation to reduce variance; 5) seasonal adjustment; and 6) 1990-based population controls on variances.

In this paper, we first give a brief background on the redesign of the CPS; discuss the design differences between PS and CPS; present estimates of various design differences; compare the expected estimates to actual estimates for the early months of 1994, where possible; summarize our results; and state a topic for immediate future research. Due to space limitations, we give only estimates of effects for design differences on the national unemployment rate. For estimates of differences in design effects on several demographic groups and on employment-to-population ratio and civilian labor force estimates, see Kostanich and Cahoon (1994).

 

Last Modified Date: July 19, 2008