Description
Families are formed at the turn of the year from persons living in the same dwelling according to the population information system of the Population Register Centre. The statistics comprise families and families with children, and their demographic data. Families are classified into families without children, married or cohabiting couples living with children, and single-parent families. Cohabiting couples are deduced from living together. The statistics contain data on the age, language, nationality and country of birth of spouses/parents, and on the age and gender of each child living at home. Families with children are those that include children under the age of 18.

Classifications used
Families are classified into married couples, unmarried couples or registered partnership couples with or without children, and into single-parent families. There is no age limit on the status of child. Families with children under the age of 18 are classified as families with children. Only families with one parent and children under the age of 18 are classified as single-parent families.
Families are usually classified by number of children into families with 1, 2, 3 and 4 or more children. Numbers of children aged, 0-6, 0-17 and 0-24 are used as children's age groups.
Since 1999, nationality, country of birth and language have been classified according to ISO standards. Prior to this, Statistics Finland's own classifications were used.
Data on families are available by diverse regional divisions based on municipalities. Data by municipal sub-region can also be provided as a charged service. The data can also be produced by regional divisions based on map co-ordinates as e.g. grid based data.
Since the statistics of 31 December 1999, the division valid on the first day of the following year has been used as the regional division. On special order, data by municipalities merged at the turn of the year can also be supplied according to the regional division valid on the last day of the previous year before the merger.

Family status
Family members are grouped by family status as follows:

In the family statistics children comprise all persons, regardless of age, who live with their parents, or the spouse's biological or adopted children, but not foster children or children in the care of the family.