Archive:European cities – the EU-OECD functional urban area definition

To be created: web-adapted introduction.

Introduction

Until recently, there was no harmonised definition of ‘a city’ for European and other countries member of the Organisation for Economic Cooperation and Development (OECD). This undermined the comparability, and thus also the credibility, of cross-country analysis of cities. To resolve this problem, the OECD and the European Commission developed a new definition of a city and its commuting zone in 2011.

This new OECD-EC definition identified 828 (greater) cities with an urban centre of at least 50 000 inhabitants in the EU, Switzerland, Croatia, Iceland and Norway. In addition, this methodology identified a further 492 cities in Canada, Mexico, Japan, Korea and the United States. This Regional Focus describes on the European cities, for information on the other cities, see Redefining urban: a new way to measure metropolitan areas (OECD 2012) (1). Half of these European cities are relatively small with a centre between 50 000 and 100 000 inhabitants. Only two are global cities (London and Paris). These cities host about 40 % of the EU population. These cities do not include towns and suburbs which cover another 30 % of the EU population according to the revised degree of urbanisation classification.

Each city is part of its own commuting zone or a polycentric commuting zone covering multiple cities. These commuting zones are significant, especially for larger cities. The cities and commuting zones together (called Larger Urban Zones) account for 60 % of the EU population.

Table, Figure or Map X: Full title of the Table, Figure or Map - Source: Eurostat (educ_ilang)

A harmonised definition

Definition of a city

This new definition works in four basic steps and is based on the presence of an ‘urban centre’ a new spatial concept based on high-density population grid cells.

Step 1: All grid cells with a density of more than 1 500 inhabitants per sq km are selected (Figure 1.1.). <1> www.oecd.org/gov/regional/measuringurban </1>

Step 2: The contiguous (2) high-density cells are then clustered, gaps (3) are filled and only the clusters with a minimum population of 50 000 inhabitants (Figure 1.2) are kept as an ‘urban centre’. <2> Contiguity for high-density clusters does not include the diagonal (i.e. cells with only the corners touching).</2> <3> Gaps in the high-density cluster are filled using the majority rule iteratively. The majority rule means that if at least five out of the eight cells surrounding a cell belong to the same high-density cluster it will be added. This is repeated until no more cells are added </3>

Step 3: All the municipalities (local administrative units level 2 or LAU2) with at least half their population inside the urban centre are selected as candidates to become part of the city (Figure 1.3).

Step 4: The city is defined ensuring that 1) there is a link to the political level, 2) that at least 50 % of city the population lives in an urban centre and 3) that at least 75 % of the population of the urban centre lives in a city (Figure 1.4) (4). <4> This step is not included in the non European cities.</4>

In most cases, as for example in Graz, the last step is not necessary as the city consists of a single municipality that covers the entire urban centre and the vast majority of the city residents live in that urban centre. For 33 urban centres stretching far beyond the city, a ‘greater city’ level was created to improve international comparability (see below for more detail). To ensure that this definition identified all relevant centres, the national statistical institute were consulted and minor adjustments were made where needed and consistent with this approach.

Definition of a commuting zone

Once all cities have been defined, a commuting zone can be identified based on commuting patterns using the following steps: ■■ If 15 % of employed persons living in one city work in another city, these cities are treated as a single city. ■■ All municipalities with at least 15 % of their employed residents working in a city are identified (Figure 2.2) ■■ Municipalities surrounded (5) by a single functional area are included and non-contiguous municipalities are dropped (Figure 2.3). The Larger Urban Zone consists of the city and its commuting zone. <5> Surrounded is defined as sharing 100 % of its land border with the functional area.</5> Figure 2.1-3 How to define a commuting zone – City and its commuting zone (Genova)

For more details on the sources and reference years for the commuting zones please consult the annex.

What does it tell us about cities in Europe?

This definition allows for the first a comparison of the number of cities and the share of population in them on a harmonised basis across Europe. Each country has its own method of defining a city based on a wide range of criteria. These criteria often include population size and density, but also more functional or historic ones such as having urban functions, being a recipient of national urban policy funds or having received city rights through a charter sometime between the Middle Ages and today. For example, in the UK city status is conferred by the Monarch since 16th century and still is today. This does lead to some surprising cities, such as St Davids in Wales with less than 2 000 inhabitants. Comparing the number of cities based on national definitions across countries is hopelessly distorted by difference in methodology.

This new definition does not rely on functions, funding or feudal history, but is purely based on population size and density. To a large extent, the definition identifies the European urban hierarchy as most people would expect it, but with some surprises here and there (see Figure 3). The two largest cities in the EU are, of course, London and Paris. The six cities with an urban centre of around three million inhabitants however are novel: Athens, Berlin, Madrid, Barcelona, Naples and Milan, because in four out of these six cities the population of their administrative city is so much smaller than the population of their urban centre. For Athens, Barcelona, Naples and Milan, a greater city level was created to better capture this centre (see below). Among the eighteen cities with a centre between one and two million inhabitants, there are six cities for which a ‘greater city’ level needed to be created. Figure 3 Number of cities per country and per urban centre size, 2006

Further down the city list, there are still some surprises with some nationally defined cities missing and some other municipalities included (see annex). In part, this is because only the top half of the urban hierarchy has been identified here. Small and medium-sized towns with a centre with between 5 000 and 50 000 inhabitants are not yet defined in a harmonised manner. A new ESPON (www.espon.eu) project ‘TOWN’ will search for a harmonised definition of the bottom half of the urban hierarchy. Mostly, the surprises are due to the difference in the population of an urban centre and the administrative city.

Looking at the number of cities shows that some countries have only one city (Luxembourg, Malta and Iceland) or two cities (Slovenia and Cyprus). The three most populous countries also have the most cities with over one hundred cities in Germany, the UK and France. Figure 4 Share of population per country per city size and commuting zone, 2006

Overall, in the EU two out of five residents live in city with a centre of 50 000 inhabitants and one out of five lives in a commuting zone of these cities (see Figure 4). Together about three out of five residents live in a city or a commuting zone (or Larger Urban Zone). This share, however, changes substantially between countries. Following this definition, Slovakia and Romania have the lowest shares of their population living in a city or its commuting zone (33 % and 38 %). Germany, the UK and the Netherlands have the highest shares of population living in a city or commuting zone (73-74 %), not considering Luxembourg and Cyprus which have very high shares due to their small size.

Detailed methodology

This section describes three adjustments that were made to municipalities identified as part of city based on their share of population in an urban centre.

Urban centre is much bigger than the city

In some cases, the urban centre is stretches far beyond the boundaries of city. This problem is called an ‘underbound’ city, in other words the city is too small relative to its centre. This can be resolved in three ways: 1) create a greater city level, 2) cover a single centre with multiple cities and 3) a combination of these two approaches.

Creating a greater city

To better capture the entire urban centre, a ‘greater city’ level can be created. This is a fairly common approach and several greater cities already exist: Greater Manchester, Greater Nottingham etc. This level was created for ten capitals and 23 other large cities (see Figure 5).

The list below also indicates that underbound cities are more common in some countries. For example, nine out of the ten Swiss cities now have a greater city level.

Figure 5 List of Urban Audit greater cities in Europe

In seventeen cases, the greater city contains a single city. Athens is a clear example of such an approach (see Figure 6). The urban centre (in black) is much bigger than the city (in red). A greater city level was added (blue outline), which captures a far greater share of the population of the urban centre.

Figure 6.1-4 High density cells, urban centre, city and greater city (Athina)

Sixteen greater cities include multiple cities. In most cases, the greater city equals the combination of two or more cities. The greater city of Porto, for example, is made up of five cities (Porto, Vila Nova de Gaia, Gondomar, Valongo and Matosinhos, see Figure 7). In a few cases, the greater city includes several cities and other communes, as for example in Rotterdam, Helsinki, Milan and Naples.

Figure 7.1-4 High density cells, urban centre, cities and greater city (Porto)

Covering a single urban centre with multiple cities

In some cities, instead of creating a ‘greater city’ level, multiple cities were used to cover one urban centre. For example, Poole and Bournemouth share a single urban centre, but no ‘greater city’ level was created, just two separate cities (see Figure 8). This was only done in few cases at the request of the National Statistical Institutes, when the cities were similar in size and governed separately.

Figure 8.1-4 High density cells, urban centre and cities (Bournemouth - Poole)

Data sources and availability

Context

Further Eurostat information

Publications

Title of the publication

Main tables

Title of top Main tables folder, see:

Title(s) of second level folder (if any)

Title(s) of third level folder (if any)

Database

Title of top Database folder, see: