As Ericksen (2000:207) summarizes, “whole-household omissions” are easy to understand conceptually; they occur when an entire housing unit is left off the Master Address File and, hence, does not receive a questionnaire. However:
Some housing units are missed because no one finds the building. Others are missed because they are located in structures that appear to contain only one residence but actually contain several. For instance, a three-story house, originally built for one family, is converted into apartments. From the outside, the census-taker sees only one door and one mailbox, and he or she does not search for nor find the extra housing units to update the mailing list. …Housing units for the very poor can be be hard to find. Old apartment buildings, often located in high-crime areas, may not have separate mailboxes or identifiable numbers for the individual apartments. Many very poor people, frequently undocumented aliens, live in places like garages and tents located in the backyards of friends or relatives. Their addresses are not listed and they are not counted.
In the balance of this chapter we briefly consider two special cases where the nature of housing stock precludes an easy determination of residence.
The earliest census enumerator instructions recognized the need to account for the population found in inns and other public houses. Through the 19th century, public houses and hotels tended to be places where people spent relatively long stretches of time; the concept of the hotel as a primarily short-term and transient residential location is a more modern one, particularly spurred on by the emergence of motor lodges or motels in the mid-20th century. The enumerator instructions for the 1900 census were the first to acknowledge the temporary, “transient guests of a hotel”; these “are not to be enumerated as of the hotel, unless they are likely otherwise to be omitted from the enumeration.” Instead, only boarders or employees “who regularly sleep” at the hotel (including the owner) were to be counted at the hotel.
The 1930 enumerator instructions acknowledged the basic problem of hotel housing stock: “the distinction between an apartment house and an apartment hotel, and in turn between an apartment hotel and a hotel devoted mainly to transients, will often be difficult to establish.” Having laid out the basic challenge, though, the instructions prescribed a rather confusing rule:
All of the persons returned from a hotel should likewise be counted as a single “family,” except that where a family of two or more members (as a husband and wife, or a mother and daughter) occupies permanent quarters in a hotel (or an apartment hotel), it should be returned separately, leaving the “hotel family” made up principally of individuals having no other family relations.