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- 4 - TECHNICAL NOTE These data and other information on work schedules were obtained from a supplement to the May 2004 Current Population Survey (CPS). The CPS is a monthly sample survey of about 60,000 households conducted by the U.S. Census Bureau for the Bureau of Labor Statistics (BLS), principally to gather information on employment and unemployment for the nation. Respondents to the May 2004 supplement answered questions about flexible and shift sched- ules, the reasons for working particular shifts, the beginning and ending hours of work, formal flexitime programs, home-based work, and other related topics. The data in this release cover the incidence and nature of flexible and shift schedules and pertain to wage and salary workers who usually worked 35 hours or more per week on their principal job. The data exclude all self- employed persons, regardless of whether or not their businesses were incorp- orated. The May 2001 data presented in this release have been revised to reflect the introduction of Census 2000-based population controls and thus may differ from previously published estimates which were based on population controls derived from the 1990 census. The introduction of the Census 2000-based population controls increased the May 2001 employment levels but had relatively little impact on proportions and percents derived from the employment levels. Sample results from the CPS are weighted up to independent estimates of the population by sex, age, race, and Hispanic or Latino/non-Hispanic ethnicity. The weights, or population controls, are developed using counts of the civilian noninstitu- tional population derived from the decennial census and are updated using information from administrative records. Information in this release will be made available to sensory impaired individuals upon request. Voice phone: 202-691-5200; TDD message referral phone number: 1-800-877-8339. Reliability of the estimates Statistics based on the CPS are subject to both sampling and nonsampling error. When a sample, rather than the entire population, is surveyed, there is a chance that the sample estimates may differ from the "true" population values they represent. The exact difference, or sampling error, varies depending on the particular sample selected, and this variability is measured by the standard error of the estimate. There is about a 90-percent chance, or level of confidence, that an estimate based on a sample will differ by no more than 1.6 standard errors from the "true" population value because of sampling error. BLS analyses are generally conducted at the 90-percent level of confidence. The CPS data also are affected by nonsampling error. Nonsampling error can occur for many reasons, including the failure to sample a segment of the population, inability to obtain information for all respondents in the sample, inability or unwillingness of respondents to provide correct information, and errors made in the collection or processing of the data. For a full discussion of the reliability of data from the CPS and for information on estimating standard errors, see the "Explanatory Notes and Estimates of Error" section of Employment and Earnings. Concepts Data on flexible schedules, shift work, and beginning and ending hours of work were obtained from the following questions: Beginning and ending hours of work. At what time of day do you begin work on your (main) job most days? 1. __hour __minutes A.M./P.M. 2. It varies At what time of day do you end work on your main job most days? 1. __hour __minutes A.M./P.M. 2. It varies Flexible schedules. Do you have flexible work hours that allow you to vary or make changes in the time you begin and end work? 1. Yes 2. No Formal flexitime programs. (If the respondent answers "yes" to the above question on flexible hours, the following question is then asked.) Is your flexible work schedule part of a flexitime or other program offered by your employer? 1. Yes 2. No Shift work. On your (main) job, do you usually work a daytime schedule or some other schedule? 1. A daytime schedule (Anytime between 6 A.M. to 6 P.M.) 2. Some other schedule (If the respondent answers "some other schedule" to the above question, then the following question is asked to determine the shift worked.) Which of the following best describes the hours you usually work at this (main) job? 1. An evening shift (Anytime between 2 P.M. and midnight) 2. A night shift (Anytime between 9 P.M. to 8 A.M.) 3. A rotating shift--one that changes periodically from days to evenings or night 4. A split shift--one consisting of two distinct periods each day 5. An irregular schedule 6. Some other shift Reason for alternative shift. What is the main reason why you work this type of shift? (Interviewer reads all.) 1. Better arrangements for family or child care 2. Better pay 3. Allows time for school 4. Could not get any other job 5. Local transportation or pollution control program 6. Nature of the job 7. Personal preference 8. Some other reason