The number of persons per room, used as an index of crowding, is obtained by dividing the number of persons in the household by the number of rooms in the dwelling unit. This average was computed for each occupied dwelling unit.

Dwelling units are classified by occupancy and tenure into four groups: Owner occupied; tenant-occupied; vacant, for sale or rent; and vacant, not for sale or rent. Dwelling units are classified as occupied if occupied at the time of enumeration by households enumerated at their usual place of residence. The relatively small group classified as vacant, not for sale or rent" includes dwelling Units that were neither occupied nor available for sale or rent at the time of enumeration because they were being held for absent households, and dwelling units that were occupied temporarily by nonresident households.