Women's representation in physics lags behind most other STEM disciplines. Currently women make up about 13% of faculty members in all degree-granting physics departments, and there are physics departments with no women faculty members at all. In this report, we consider whether or not the lack of a woman among its faculty is sufficient evidence of a hiring bias. Using simulation analysis, we find that the existence of all-male departments is largely due to the representation of women in physics and to the number of faculty members in a single department. Even if half of physics faculty members were women, we would still find over 100 departments with all male or all female faculty members. While counting the number of departments with no women is not a valid measure of equity, we do not mean to provide a convenient explanation for departments that have no women. Instead, the issue of equity in physics is more complex and nuanced and should not be distilled into any single measure.