PX-Web API

From the dataset abstract

Nordstat: statistics on largest Nordic cities contains statistics on population and population change, employment, housing and construction, education, air traffic and local elections.

Statistics are updated yearly and most time series are available from 1990s onwards. Database is maintained by the city of Helsinki and local administrations in Nordic countries provide the information.

Source: Nordstat: tilastoja Pohjoismaiden suurimmista kaupungeista ja kaupunkiseuduista