Prior to 1997, changes in the statutory order of succession were classified as adopted children in the population statistics, although no actual adoptions were made. From the 1997 statistics, only actual adoptions have been recorded as adoptions.
All persons entered in the Population Register are indicated a country of birth, which is determined on the basis of the mother's permanent home country at the time of birth. This means, for example, that the country of birth of Estonian immigrants born before Estonian independence is the Soviet Union. Similarly, the country of birth of people who were born in areas that Finland has subsequently ceded is Finland even though the area no longer is Finnish territory. Country of birth is indicated according to the form of government at the time of birth.
The information on marital status is derived from the Population Information System of the Population Register Centre. It should be noted that common-law marriage or cohabiting is not a marital status. People representing all marital status categories may be cohabiting, including those who are still officially married.
The current divorce regulations no longer recognise the concept of legal separation. Those persons who are legally separated on the basis of the old divorce provisions prior to 1 January 1988 and still living apart have been slotted under married persons in the statistics.
Same-sex couples have been able to register their partnership in Finland as of 1 March 2002. For reasons of data protection, in municipal tables those living in a registered partnership are classified together with married persons, as are those divorced or widowed from a registered partnership with divorced and widowed persons.
The classification of marital status is as follows:
The information about sex has been obtained from the Population Information System.