Hourwage and earning of 0

Why do respondents have an hourly wage of 0? are these respondents who were not employed?

According to the original BLS data dictionaries, an hourly wage of 0 is a valid response. Though these occurrences are rare, they are in-universe cases (employed), according to the universe for HOURWAGE. These cases are difficult to interpret so they may be indications of low data quality and should be treated cautiously and potentially dropped from an analysis.