Satellite image of theNew York metropolitan area, the largest metropolitan area in the United States and one of the largest in the world, withLong Island in the east andManhattan at the center of the densest part of the imageA metropolitan area usually includes a main city and a series of smaller satellite cities as can be seen in this map ofMadrid's metropolitan area (click on the map to enlarge it).
In theUnited States, the concept ofmetropolitan statistical areas has gained prominence. The area of the GreaterWashington metropolitan area is an example of statistically grouping independent cities and county areas from various states to form a larger city because of proximity, history and recenturban convergence. Metropolitan areas may themselves be part of a greatermegalopolis. For urban centres located outside metropolitan areas that generate a similar attraction at a smaller scale for a region, the concept of aregiopolis and a respective regiopolitan area, or regio, was introduced by German professors in 2006.[8] In the United States, the termmicropolitan statistical area is used.
A metropolitan area combines anurban agglomeration with the contiguous built-up areas, which are not necessarily urban in character but are closely bound to the center by employment or other commerce. These outlying zones are sometimes known as a commuter belt and may extend well beyond the urban zone to other political entities. For example,East Hampton, New York, onLong Island is considered part of theNew York metropolitan area.
In practice, the parameters of metropolitan areas, in both official and unofficial usage, are not consistent. Sometimes they are little different from an urban area, and in other cases, they cover broad regions that have little relation to a single urban settlement; comparative statistics for metropolitan areas should take this into account. The term metropolitan can also refer to acounty-levelmunicipal government structure, with some shared services between a central city and its suburbs, which may or may not include the entirety of a metropolitan area. Population figures given for one metro area can vary by millions.
There has been no significant change in the basic concept of metropolitan areas since its adoption in 1950,[11] although significant changes in geographic distributions have occurred since then, and more are expected.[12] Because of the fluidity of the term "metropolitan statistical area", the term used colloquially is more often "metro service area", "metro area", or "MSA", taken to include not only a city but also the surrounding suburban, exurban and sometimes rural areas, all of which the city is presumed to influence. Apolycentric metropolitan area contains multiple urban agglomerations not connected by continuous development. In defining a metropolitan area, it is sufficient that a city or cities form a nucleus with which other areas have a high degree of integration.
A metropolitan area is commonly known and characterized by a high concentration inservice sector labor and enterprises.[13][14]Macroeconomics views metropolitan areas astrade regions of economic significance.[15]
Since, presently, urban data are based on arbitrary definitions that vary from country to country and from year or census to the next, making them difficult to compare, an Urban Metric System (UMS) has been conceived that could correct the problem,[16] since it allows computing the urban area limits and central points, and it can be applied in the same way to all past, present and future population and job distributions. It is based on vector field calculations obtained by assuming that, in a given space, all inhabitants and jobs exert the same attractive forceA and repulsive forceR. The net force (A -R) exerted by each inhabitant or job is given by [1/(1 +d)] - [1/(β +d/2)], whered = distance andβ is the only parameter. UMS distinguishes the following types of urban areas, each type corresponding to a given value ofβ:
Urban area
Distance at which the attractive force = the repulsive force
Value ofβ
1
Central city
10 km
6
2
Agglomeration
20 km
11
3
Metropolis
40 km
21
4
Patropolis
80 km
41
5
Megalopolis
160 km
81
6
Urban system
320 km
161
7
Urban macrosystem
640 km
321
8
Continental system
1,280 km
641
9
Intercontinental system
2,560 km
1,281
10
World system
5,120 km
2,561
UMS has been applied to some Canadian cases since 2018, but the data presented in this article are still based on the various existing national definitions, which are disparate.
TheGreater Johannesburg metropolitan area is the fourth largest metropolitan area inSouth Africa. Its population was over 9.6 million as of the 2011 South Africa Census, in contrast to its urban area, which consisted of approximately 7.9 million inhabitants as of 2011. Conversely,metropolitan municipalities in South Africa are defined as commonly governed areas of a metropolitan area. The largest such metropolitan municipal government entity in South Africa is theCity of Johannesburg Metropolitan Municipality, which presided over nearly 5 million people as of 2016. However, the Greater Johannesburg metropolitan area houses roughly ten times the population of its core municipal city ofJohannesburg, which contained 957,441 people as of the 2011 census.
In Brazil, the termsmetropolitan area (Portuguese:região metropolitana) andurban agglomeration (aglomeração urbana) have specific meanings. They are defined by federal and state legislation as collections ofmunicipalities focused on "integrating the organization, planning and execution of public functions of common interest".[17] Anintegrated development area (região integrada de desenvolvimento) is one of the two above structures that crosses state (orFederal District) boundaries.
The IBGE defines also "Immediate Geographic Areas" (formerly termedmicroregions) which capture the region "surrounding urban centers for the supply of immediate needs of the population".[18] Intended for policy planning purposes, as of March 2021 census data is not tabulated on the level of these Areas, but instead at themunicipality or state level.[19]
In Canada, acensus metropolitan area (CMA) orcensus agglomeration (CA) consists of one or more neighboring municipalities centered around a core population. A CMA requires a total population of at least 100,000, with 50,000 or more residing in the core, while a CA requires a core population of at least 10,000. Both are determined using data from Canada's Census of Population Program, and surrounding municipalities must demonstrate strong economic integration with the core, measured by commuting patterns.[20]
There are three metropolitan areas in Chile, the biggest and most important one is the Gran Santiago in the Santiago Metropolitan Region, with over 7 million inhabitants, making it the largest and most populated urban area in Chile. The other two metro areas are Gran Valparaiso in the Valparaiso Region with almost a million inhabitants, and Gran Concepción in the Bio Bio Region, with a population of about a million people living in it.Smaller "metropolitan" areas are known as conurbations. Conurbaciones tend to have a bit over 200.000 inhabitants to be considered as such. An example is the Conurbacion de Rancagua, which considers the area shared by the city of Rancagua, and the adjacent smaller towns of Machalí, Gultro and Graneros.
Metropolitan areas are known aszonas metropolitanas in Mexico. The National Population Council (CONAPO) defines them as:[21]
a set of two or more municipalities where a city with a population of at least 100,000 is located, and whose urban area, functions and activities exceed the limits of the municipality.
municipalities with a city of more than 500,000 inhabitants, or a city of more than 200,000 inhabitants located in the northern and southern border areas and in the coastal zone.
municipalities where state capitals are located, if they are not already included in a metropolitan zone.
As of 2018, there are 74zonas metropolitanas in Mexico. 75.1 million people, 62.8% of the country population, live within a metropolitan area.[21]
The Office of Management and Budget defines a Metropolitan Statistical Area as one or more adjacentcounties orcounty equivalents that have at least oneurban area of at least 50,000 population, plus adjacent territory that has a high degree of economic andsocial integration with the core as measured bycommuting ties. The OMB then defines a Combined Statistical Area as consisting of various combinations of adjacent metropolitan and micropolitan statistical areas with economic ties measured by commuting patterns. The Office of Management and Budget further defines a core-based statistical area (CBSA) to be a geographical area that consists of one or more counties (or equivalents) anchored by an urban center of at least 10,000 people plus adjacent counties that are socioeconomically tied to the urban center by commuting.
TheMelbourne metropolitan area in Australia seen at night from the International Space Station
TheAustralian Bureau of Statistics usesGreater Capital City Statistical Areas (GCCSAs), which are geographical areas designed to represent the functional extent of each of the eight state and territory capital cities. They were designed to reflect labor markets, using the 2011 Census "travel to work" data. Labor markets are sometimes used as proxy measures of the functional extent of a city as it contains the majority of the commuting population. GCCSAs replaced "Statistical Divisions" used until 2011.[23]
Other metropolitan areas in Australia include cross border cities or continuous built-up areas between two or more cities that are connected by an extensive public transport network that allows for commuting for work or services.[citation needed]
InChina, there used to be no clear distinction betweenmegalopolis (城市群, lit. city cluster) and metropolitan area (都市圈) untilNational Development and Reform Commission issuedGuidelines on the Cultivation and Development of Modern Metropolitan Areas (关于培育发展现代化都市圈的指导意见) on Feb 19, 2019, in which a metropolitan area was defined as "an urbanized spatial form in a megalopolis dominated by (a) supercity(-ies) or megacity(-ies), or a large metropolis playing a leading part, and within the basic range of 1-hour commute area."[25]
InIndia, a metropolitan city is defined as one with a population more than one million.[26] In policing jurisdiction, state governments can declare any city or town with a population exceeding one million as a metropolitan area as per theCode of Criminal Procedure, 1973.[27]
Dubai-Sharjah-Ajman (DSA) is a metropolitan area in the United Arab Emirates. It consists of the combined, greater urban areas of Dubai, Ajman, and Sharjah. The urban areas at the northeast end of Dubai flow into those of Sharjah, which in turn are contiguous with those of Ajman. The total population is about 5.9 million people as of 2023[29][30][31]
TheEuropean Union's statistical agencyEurostat, in partnership withOECD, has created a concept namedfunctional urban area (FUA). The FUA represents an attempt at a harmonised definition of the metropolitan area, and the goal was to have an area from which a significant share of the residents commute into the city.[32] The FUA consists of a city and its commuting zone,[33] which is a contiguous area of spatial units that have at least 15% of their employed residents working in the city.[34]
A further, derived concept is the typology ofmetropolitan regions. ANUTS 3 region (or a group thereof) is considered to be metropolitan, if at least 50% of its residents live inside a FUA with a population of 250,000 or more. NUTS 3 regions not meeting this criteria are considered to be non-metropolitan regions.[35]
France's national statistics office,INSEE, names an urban core and its surrounding area of commuter influence anaire d'attraction d'une ville [fr] (or AAV, literally meaning "catchment area of a city"), plural:aires d'attraction des villes.[36] The official translation of this statistical area in English (as used by INSEE) is "functional area".[37] The AAV follows the same definition as theFunctional Urban Area (FUA) used byEurostat and theOECD, and the AAVs are thus strictly comparable to the FUAs.[37]
The AAV replaced in 2020 the metropolitan statistical area calledaire urbaine (AU).[36] The AU, which was defined differently than the AAV, has now been discarded by INSEE and replaced with the AAV in order to facilitate international comparisons.[37]
Metropolitan regions in Germany by definition, are the eleven urban areas that are the most densely populated areas in theFederal Republic of Germany. They comprise the major German cities and their surrounding catchment areas and form the political, commercial and cultural centers of the country.
For urban centers outside metropolitan areas, that generate a similar attraction at smaller scale for their region, the concept of the Regiopolis and respectively regiopolitan area or region was introduced by German professors in 2006.
In 2001 Italy transformed 14 provinces of some of the country's largest cities intoMetropolitan Cities. Therefore, the territory of theMetropolitan City corresponds to that of a normal Italian province.
Thelist of metropolitan areas in Sweden is collated based on statistics of commuting between central municipalities and surrounding municipalities and taking into account existing planning cooperation in the country's three geographic regions.[38] They were defined around 1965. In 2005, a number of further municipalities were added to the defined areas.
The word metropolitan describes the central municipality governing local services in a province with more than 750.000 residents inTurkey, likeIstanbul and its metropolitan municipality, theIstanbul Metropolitan Municipality. There are 30 officially defined "metropolitan municipalities" in Turkey.[39] This classification, however, is only used for administrative purposes, and sometimes contradicts the colloquial use of the term "metro area". As an example, Gebze, a district inKocaeli province and thus in the jurisdiction of the Kocaeli Metropolitan Municipality, is arguably within the metro area of Istanbul with many of its residents commuting to Istanbul for work and the Marmaray, a commuter rail line, extending into the district. The district however, as previously mentioned, is not a part of Istanbul's provincial limits, and thus not subject to the jurisdiction of its metropolitan municipality. The word metropolitan (municipality) is generally only used as an administrative distinction in Turkey.
^"Metropolitan Cities of India"(PDF).Central Pollution Control Board. National Informatics Centre. p. 3. Archived fromthe original(PDF) on 23 September 2015. Retrieved28 July 2014.
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