Readers Guide

Typologies of regions with respect to population or other functions


An individual city is defined by an administrative border of a local government. A functional urban area (see below) encompasses more than the urban core of the main city. In this report, for simplicity, a city refers to a functional urban area, and if of large size, is referred to as a metropolitan area (see below). Where the term refers to an administrative city, this will be made explicit.

Functional regions

are geographic areas defined by their economic and social integration rather than by traditional administrative boundaries. A functional region is a self-contained economic unit according to the functional criteria chosen (for example, commuting, water service or a school district).

Functional urban areas

are defined as densely populated municipalities (urban centres) and adjacent municipalities with high levels of commuting towards the densely populated urban centres. Commuting zones, according to a definition developed by the OECD and the European Union. Functional urban aread can extend across administrative boundaries. The OECD tracks functional urban areas of 50 000 inhabitants and more.

Metropolitan areas

are defined as those functional urban areas with a population of over 250 000. There are 628 metropolitan areas in the 33 OECD countries with data; of these, 99 had a population greater than 1.5 million in 2016.

Regions (TL2 and TL3)

are classified by the OECD into two territorial levels that reflect the administrative organisation of countries. The OECD’s large regions (TL2) represent the first administrative tier of subnational government, such as the Ontario region in Canada. OECD small (TL3) regions are contained within a TL2 region. For example, the TL2 region of Aquitaine in France encompasses five TL3 regions: Dordogne, Gironde, Landes, Lot-et-Garonne and Pyrénées-Atlantiques. In most cases, TL3 regions correspond to administrative regions, with the exception of Australia, Canada, Germany and the United States.

TL3 regional typology

TL3 regions have been classified as: predominantly urban (PU), intermediate (IN) and predominantly rural (PR) based on the percentage of regional population living above certain thresholds of population densities. The terms urban, intermediate and rural are used to refer to these categories. An extended typology distinguishes between regions that are predominantly rural and close to a city, and predominantly rural regions that are remote. The distinction is based on the driving time to the nearest urban centre with at least 50 000 inhabitants for a certain share of the regional population. Due to lack of information on the road network, the predominantly rural regions in Australia, Chile and Korea have not been classified as remote or close to a city.

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