Under the citizenship act, a person who is to be granted Norwegian citizenship - in addition to other conditions - must normally have had to stay in Norway for a certain number of years. This length of stay varies according to the status of the applicant. It is the Norwegian Directorate of Immigration that decides and calculates the length of stay that applies to the individual.

Population register data also provides the opportunity to calculate a residence time, e.g. as time from first immigration/birth in Norway. We have used population register data. The distribution 0-8 years has been chosen in order to delimit by a good margin those who have switched to Norwegian citizenship relatively early after the requirement of residence has been met.