In the earlier period, the question was, "Was health insurance offered to you through your workplace?" In the later period, the question was, "Regarding your job or work last week, was health insurance offered to you through your workplace?"

The filter variable for HIATWORK, EMPSTAT did not initially distinguish between people working at a job or business for pay and not for pay in the earlier period; both were implicitly combined in the category "working at a job or business." Beginning in 2001, EMPSTAT has two separate categories for people working during the preceding week (i.e., "working for pay at a job or business" and "working, but not for pay, at a job or business"). The universe for HIATWORK was affected by this change only to the extent that people working, but not for pay (e.g., working for a family farm or business without receiving wages), tended to underreport themselves as "working" in the earlier period.