In the 1990-2004 Census-internal SIPP panels, a value for sex is included on each wave file. Thus, there are actually as many sex variables as there are waves of the survey and some changes occur across waves as a result of data collection error. Sex is selected from the array of variables sex1-sex{max number of waves} in which the wave corresponds either to the month in which marital status is first observed (for those without spouses during the course of the SIPP) or to the month in which the respondent's spouse is assigned instead of from a fixed point in the survey. Thus when a spouse is never assigned, an individual's gender comes from the first wave where they report being not married. For individuals who are assigned a spouse, gender comes from the first wave where they reveal their spouse. Finally, an indicator variable for males was created from the categorical sex variable for analytic convenience. This variable is unsynthesized on the SSB and is never missing so there are no imputed values in the Completed Data.

0	Female
1	Male