Differences Between Decennial Census and LAUS Data

The Census Bureau released Demographic Profile state and substate data from the 2000 Census on a state-by-state basis between May 7 and June 4, 2002. These tabulations included data on socioeconomic characteristics and labor force status for states, metropolitan areas, counties, and smaller units of geography. The Census-based labor force estimates may differ from the official labor force data released by the Bureau of Labor Statistics (BLS) because of differences in methodology, design, and data collection.


Every ten years, the Bureau of the Census conducts a census of the population. It is a snapshot of the population for one moment in time (April 1 of the Census year). The main purpose of this Census is to provide the population count needed for the re-apportionment of seats in the House of Representatives and determination of State legislative district boundaries.

The economic characteristics data from the 2000 Census are based on a systematic sample of approximately 17 percent of the Census households (i.e., every second, fourth, sixth, or eighth housing unit, depending on the population of the area). The questions on the long form address economic characteristics issues, including labor force. This invites comparison with the official labor force data from BLS that are developed by the Local Area Unemployment Statistics (LAUS) program.

The Current Population Survey (CPS) has been the source of the official estimates of unemployment for the nation for more than half a century. The survey has been greatly expanded and improved over the years, but the basic concepts of employment and unemployment—reviewed periodically by high-ranking commissions—have remained substantially unaltered. At present, the CPS is the sole and official source of the monthly statistics on unemployment for the nation. It is the main input to the estimating models that produce the official monthly labor force estimates for all states, the District of Columbia, New York City, and the Los Angeles-Long Beach-Glendale metropolitan division. Through the LAUS methodology, the CPS also affects estimates for nearly 7,200 substate areas.

Information on unemployment has been obtained in decennial censuses since the late nineteenth century, although the current concepts were not introduced until 1940, concurrent with the origins of the CPS. There have always been differences in measured unemployment between the CPS and the Census. Prior to 1990, however, the Census-based estimates of the number unemployed had typically been lower than those from the CPS, although the gap had generally been closing over time. In 1950, the Census count of unemployed persons for the nation was about 19 percent lower than the April 1950 figure from the CPS. The gap shrank to about 4 percent in 1960 and about 1.5 percent in 1970, before widening slightly, to about 3 percent (lower) in 1980. Census unemployment rates were below or about the same as those from the CPS from 1950 to 1980. In 1990, for the first time, the Census-based estimates of both the number of unemployed and the unemployment rate were considerably higher than the CPS figures, with the relative size of the gap being similar to that obtained in 1950, but in the opposite direction.

Conceptual and methodological differences between the CPS and Census

  • Interview-controlled environment versus self-enumeration

    All data from the CPS are gathered by trained field interviewers through personal visits and telephone interviews. For the most part, decennial Census data are self-reported. That is, individuals fill out a questionnaire by themselves. There are generally no interviewers to clarify survey questions and probe for more accurate and detailed responses, as is the case in the CPS.

  • Specific versus general survey questions

    The CPS currently uses 13 specific, detailed questions to determine one’s employment status. In the Census, the questions are fewer—only six. The enhanced specificity in the CPS is designed to avoid misclassifications.

    This is particularly relevant to the CPS “active job search” concept, whereby respondents are probed to determine exactly what active job hunting measures, if any, they have undertaken. Passive activities, such as simply perusing classifieds, do not result in a person being classified as unemployed in the CPS. However, given the self-enumeration aspect of the Census, a person might count such passive activities as “looking for work.”

  • Intensive versus limited quality control of data collection

    CPS interviewers are trained extensively before going out into the field, and proficiency checks are conducted regularly. In addition, each month, a portion of the households in the sample are reinterviewed, and the results are used to control and measure the quality of the data. In the Census, the extent to which the quality of the data can be controlled or evaluated is much more limited.

  • Definite versus variable reference week

    The CPS questions for determining current employment status relate to a specific reference week, the week including the 12th of the month (or, in the case of job search, the 4 weeks preceding the survey week). The Census questions relate to the calendar week preceding the date that the questionnaires were completed (in the case of job search, the 4 weeks preceding the date of reporting).

  • First interview reporting bias

    In the CPS, households are in the sample for 4 consecutive months, out of the sample for the following 8 months, and then interviewed again for 4 months. There is a tendency among households surveyed for the very first time (first month in sample) and among those surveyed after the 8-month intermission (fifth month in sample) to report higher levels of unemployment than those who have been in the survey for several consecutive months. This phenomenon affects one-fourth of the CPS sample. In the Census, virtually every household is reporting for the first time. Thus, any upward bias in unemployment associated with first interview could conceivably affect the entire Census.

    In addition to the above mentioned factors that not only pertain to the 2000 Census, but also are relevant to several of the prior Censuses, the 2000 Census was negatively impacted by a data collection problem pertaining to group quarters, particularly in towns with high percentages of college dormitory residents. In particular, the form used to collect labor force status information in group quarters (the Individual Census Report, or ICR) was processed such that a very large number of incomplete forms were systematically and erroneously allocated to unemployment, resulting in implausibly high unemployment rates being reported for these areas. While the Census Bureau has acknowledged this problem and has undertaken some study of the issue, no correction factors have been developed to produce more accurate estimates for these areas.

Additional information

For information on the decennial Census, visit the Census Bureau.

For more information on the CPS, see Current Population Survey Design and Methodology (Technical Paper 63 Revised) ( PDF 3.11MB, 228 printed pages).

For more information on the LAUS program visit State and Local Unemployment Rates.


Last Modified Date: September 29, 2005