Do enumeration rules differ between the different NAPP censuses?
Yes, enumeration rules differ between the different censuses, which have some implications for understanding patterns of household relationships.
A de jure census involves enumerating the population at their permanent residence. Thus, people temporarily away from home are enumerated by the people remaining at home who provide the census enumerator their information. A de facto census enumerates people where they are found on a census night. Norway and Iceland were unusual in using both rules for some censuses. This means some people are enumerated twice and identified as such in the data. Users should exclude one set of similar individuals for accurate population statistics. For the Norway 1900 census, the individuals who are enumerated twice are identified in the variable RESIDENT. More information on the Norwegian census can be found here.
For Sweden, the censuses were not taken by census workers going out with a questionnaire and interviewing people in their homes on a particular day. Instead the censuses were taken by vicars and parish priests who made extracts from the already existing church examination records (1860-1890) and parish books (1900-1945).