The purpose of regional classifications used in statistics is to describe regional variations of various phenomena and regional structure. As most regional classifications, the division of sub-regional units is based on the administrative regional division.
The division of sub-regional units was adopted in 1994 as a basic division of the acts on regional policy (Act on regional development 1135/93). The criteria used for forming sub-regional units have mainly been cooperation between municipalities and employment.
Municipalities, sub-regional units, regions and the statistical grouping of municipalities are the primary regional classifications used in Finland's statistical system. Other municipality-based regional classifications used in statistics are major regions, Regional State Administrative Agencies (AVI) and Centres for Economic Development, Transport and the Environment (ELY centres). Types of municipalities include the cost-of-living classification, financial capacity classification, language distribution classification and municipality form classification.