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:
Citizenship refers to a person's legal nationality in a certain country. Citizenship is usually determined at birth, but it may be changed upon moving to live in another country. A person may also be a citizen of more than one country (see Nationality Act, 359/2003 and Nationality Decree, 699/1985). Persons with both Finnish and foreign citizenship will be entered in the statistics as Finnish nationals. If a foreign national living in Finland has several nationalities, that person will be entered in the register and statistics as a national of the country on whose passport he or she arrived in the country.
The information about sex has been obtained from the Population Information System.