PERNUM is constructed to uniquely identify each person within a given household. It is available for all household members whether they were present in the household at the time of the ATUS, CPS, or both. This is the only line number variable available for each person in every household. 

LINENO was assigned to all household members present at the time of the ATUS interview. LINENO_CPS8 was assigned to all household members present at the time of the final CPS interview, 2-5 months before the ATUS interview. Because household composition could change, PERNUM, LINENO, and LINENO_CPS8 may not match.

LINENO identifies each person within a given ATUS respondent household.  It is only available for individuals who were in an ATUS respondent household at the time of the ATUS interview. ATUS respondents always have a LINENO value of 1. 

LINENO_CPS8 is a person identifier that was assigned at the time of the final CPS interview, 2-5 months before the ATUS interview.  Because household composition may have changed between the dates of the CPS and ATUS interviews, LINENO and LINENO_CPS8 may not match. 

PERNUM is an additional person identifier that is available for all person records in the dataset.

WT06 provides ATUS respondent weights based on the weighting methodology introduced in 2006. WT06 is available for all years and is the preferred weighting variable to use for most analyses.  It is the only weighting variable that is suitable for use in analyses that combine time use data from 2006 and later with data for earlier years.  The methodology used to construct WT06 ensures that the sums of the respondent weights add up to the appropriate number of weekday person-days and weekend person-days over the quarter, both for the population as a whole and for selected subpopulations. 

All ATUS weights are probability weights. Users should take care to specify them properly in their statistical packages.

Because the ATUS sample is not a simple random sample, standard errors calculated using the default options in most statistical packages will not be correct.  Calculation of correct standard errors requires the use of replicate weights.  RWT06 may be used in conjunction with WT06 for this purpose; for further details, see the description of RWT06.