The peak staff population is the number of persons working in a structure at the peak time of a workday, when the greatest number of staff are present. This number does not include persons working from home in a residential building; it only counts regular employment or management positions in a structure.

A staff count applies to a particular time and needs its source and reference date. Counts from different years can reflect changes in staffing; the difference alone does not establish whether either count is correct.

Peak staff population counts staff present at the busiest time of a workday. The full capacity concerns permitted occupancy, so it answers a different question from the observed staff count.

Residential population and staff population count people through different relationships to the building. Any combined count needs to account for overlap and for the working-from-home exclusion stated above.