Size classes and city systems: million-plus cities, megacities and settlement theory

Detail

1. Census size classes of towns

• Size class: the Census of India puts every town or urban agglomeration (UA) into one of six classes by population. A UA is a town plus the built-up areas that have grown around it. The Census publishes this in its Table A-04, which shows towns and UAs by size class, with changes from 1901 to 2011 [4].

Class	Population	Common name
I	1,00,000 and above	City
II	50,000–99,999	Large town
III	20,000–49,999	Medium town
IV	10,000–19,999	Small town
V	5,000–9,999	Small town
VI	below 5,000	Very small town

• Top-heavy system: most urban people live in the biggest class, not in the many small towns.
• About 70% of India's urban population lived in Class I cities in Census 2011.
• The exact share was 70.2% in 2011, up from 68% in 2001 [5].

• Result: big cities keep pulling in people, while small towns stay small and short of services.

• Class I is very broad. It covers a city of 1 lakh and also Greater Mumbai (about 1.84 crore). So the Census and planners also use two more groups: million-plus cities and megacities.

2. Million-plus cities (metropolitan cities)

• Million-plus city / metropolitan city: a city or UA with 10 lakh (1 million) or more people.
• Growth in number:

Census	Million-plus cities/UAs
2001	35
2011	53

• Census 2011: million-plus cities held 42.6% of India's urban population [5].
• States with the most (Census 2011): Uttar Pradesh – 7 and Kerala – 7.
• Uttar Pradesh: many big cities along the Ganga plain, such as Lucknow, Kanpur, Agra, Varanasi, Prayagraj, Meerut and Ghaziabad.

• Kerala: its cities are different. Towns and villages along the coast have grown into one another (a rural–urban continuum). So many UAs, such as Kochi, Thiruvananthapuram, Kozhikode, Thrissur, Malappuram, Kannur and Kollam, cross 10 lakh.

• Link to the era: several old towns are now million-plus cities.

• Ancient: Varanasi and Prayagraj (Uttar Pradesh), Patna (old Pataliputra, Bihar) and Madurai (Tamil Nadu).
• Colonial port cities: Kolkata, Mumbai and Chennai.

3. Megacities

• Megacity: a UA with 1 crore (10 million) or more people.
• Census 2011 had three megacities:

Rank	Megacity (UA)	Population (Census 2011)	Origin
1	Greater Mumbai UA	about 18.4 million	Colonial port (west coast)
2	Delhi UA	about 16.3 million	Medieval and colonial capital
3	Kolkata UA	about 14.1 million	Colonial port and capital on the Hugli

• World picture, UN World Urbanization Prospects (WUP) 2025:
• The world had 33 megacities in 2025, up from 8 in 1975. 19 of them are in Asia [2].
• The largest cities in 2025 are Jakarta (Indonesia), nearly 42 million, then Dhaka (Bangladesh), almost 40 million, then Tokyo (Japan), 33 million [2][3].
• (NCERT: the UN ranks Delhi among the world's two largest urban agglomerations.) WUP 2025 uses a new way of counting, and Delhi is not in its top three [2][3].
• New method, Degree of Urbanisation: this sorts all land into three groups, cities, towns and rural areas. It uses the same map-based (geospatial) rules in every country, so countries can be compared fairly [2].
• Under this method, 45% of the world's 8.2 billion people live in cities (2025) [2].
• Projection to 2050: there will be 37 megacities. Hajipur (Bihar, India), Addis Ababa, Dar es Salaam and Kuala Lumpur are expected to cross 10 million. Dhaka is expected to pass Jakarta and become the largest city [2].
• India also has about 17% of the world's shrinking cities, meaning cities under 2,50,000 people whose population is falling (2025) [2].

4. Central place theory (Walter Christaller, 1933)

• Central place: a settlement that supplies goods and services to the people around it.
• Two key ideas for each good:
• Threshold: the smallest number of buyers needed to keep a shop or service running.

• Range: the farthest distance people will travel to get that good.

• How the hierarchy forms:

• Low-order goods (vegetables, a tea stall, a primary school) have a small threshold and a short range. So many small centres, close together, can supply them.
• High-order goods (a super-speciality hospital, a university, jewellery) have a large threshold and a long range. Only a few big centres, far apart, can supply them.

• Result: there are a few large high-order centres and many small low-order ones.

• Why hexagons? Circles of market areas either leave gaps or overlap. Hexagons fit together with no gaps, so every person is served. Bigger hexagons sit over many smaller ones.

• Assumptions: a flat, even (isotropic) plain, with people and buying power spread evenly, and transport equally easy in all directions.
• Uses in India:
• It explains how evenly market towns are spaced on flat plains such as the Ganga plain in Uttar Pradesh and Bihar.
• It explains periodic markets (haats and weekly markets). In poorer, thinly peopled areas, one place cannot reach the threshold every day. So traders move between villages on fixed days, as seen in tribal Jharkhand, Chhattisgarh and Odisha.

• Ancient pilgrim towns such as Varanasi and Prayagraj worked as high-order religious central places, with a very long range.

• Limits: real land has rivers, hills and coasts. Roads and railways also pull towns into lines along transport routes, which bends the hexagons out of shape.

5. Rank-size rule (G.K. Zipf, 1949)

• Rank-size rule: the city ranked n has about 1/n of the population of the largest city.
• Formula: Pₙ = P₁ / n.

• Example: if city 1 has 18 million people, city 2 should have about 9 million and city 3 about 6 million.

• India roughly fits the rule. No single city is far bigger than the rest. Mumbai, Delhi and Kolkata are close in size (Census 2011), and many regional metros sit below them.

• Why the rule fits countries like India:
• The country is large and federal, with many state capitals.
• It has several regional cores built up over history, such as Delhi in the north, Kolkata in the east, Mumbai in the west and Chennai in the south.
• Its economy is spread across many sectors.
• Result: the city sizes form a smooth ladder, not one giant city on top.

6. Primate city (Mark Jefferson, 1939)

• Primate city: a city more than twice the size of the next largest that dominates the country's politics, economy and culture.
• Examples: Bangkok (Thailand), Dhaka (Bangladesh), London (UK) and Paris (France).
• India has no primate city at the national level, so it follows the rank-size pattern instead.
• Primacy inside states: Kolkata in West Bengal is many times bigger than the next city in the state (Asansol or Siliguri).
• Cause: the colonial capital and port drew in trade, industry and migrants.
• Result: other West Bengal towns stayed small.

Feature	Rank-size pattern	Primate pattern
Who described it	Zipf, 1949	Jefferson, 1939
Size of largest city	About 2× the 2nd, 3× the 3rd	More than 2×, often much more
Typical country	Large, federal, varied (India, USA)	Small, centralised or ex-colonial (Thailand, Bangladesh)
Indian case	National level	Kolkata in West Bengal

7. Conurbation (Patrick Geddes, 1915)

• Conurbation: separate towns and cities that have grown into each other and form one continuous built-up area. Each town still keeps its own name and local government.
• How it forms: industry spreads along a river or railway → new towns grow → the gaps between them fill up → one long urban strip.
• Indian example: the Hugli industrial belt. It runs along both banks of the Hugli river (a distributary of the Ganga) in West Bengal, from Bansberia and Kalyani to Budge Budge, around Kolkata and Howrah.
• World examples: Greater London, and the Ruhr in Germany.

8. Megalopolis (Jean Gottmann, 1961)

• Megalopolis: a chain of several metropolitan regions that has merged into one huge urban belt. It is bigger than a conurbation.
• World examples:
• BosWash (Boston–Washington): this is the belt Gottmann studied. It runs along the north-east coast of the USA through New York, Philadelphia and Baltimore.

• Tokyo–Osaka: Japan's Tokaido belt.

• Possible Indian cases:

• Delhi–NCR: Delhi, Gurugram, Noida, Ghaziabad and Faridabad, spread across Delhi, Haryana and Uttar Pradesh.

• Mumbai–Pune belt in Maharashtra.

• See world-population for world urban patterns.

9. Policy link

• The Smart Cities Mission (2015) and AMRUT (2015) are mainly aimed at Class I and million-plus cities. Their goal is to improve services in a top-heavy system.
• Planners also try to give more weight to Class II–IV towns. Stronger small towns can take pressure off the megacities.

Prelims Hooks

• Census Class I = 1,00,000 and above; Class VI = below 5,000. Class II = 50,000–99,999 [4].
• Class I cities' share of urban population: 68% (2001) → 70.2% (2011) [5]. Million-plus cities' share: 42.6% (2011) [5].
• Million-plus cities/UAs: 35 (2001) → 53 (2011). Most in Uttar Pradesh (7) and Kerala (7). Trap: Maharashtra is not the top state.
• Census 2011 megacities, largest to smallest: Greater Mumbai > Delhi > Kolkata.
• UN WUP 2025: the largest cities are Jakarta > Dhaka > Tokyo. The world has 33 megacities, and Hajipur (Bihar) is projected to reach 10 million by 2050 [2].
• Theory–author pairs: Central place – Christaller (1933); Rank-size – Zipf (1949); Primate city – Jefferson (1939); Conurbation – Geddes (1915); Megalopolis – Gottmann (1961).
• Hexagonal market areas come from threshold (minimum demand) and range (maximum travel distance).
• India has no national primate city. Kolkata is primate within West Bengal.
• Hugli belt = conurbation. BosWash = megalopolis.

Mains Points

• Top-heavy urban system (GS-I):
• Class I cities hold 70.2% of the urban population (2011) [5].
• Cause: jobs, services and investment are concentrated there.
• Effects: slums, traffic jams, water stress and pressure on land in the metros, while small towns fall behind.

• Policy response: build up Class II–IV towns as growth centres, and target Smart Cities Mission and AMRUT funds well.

• Rank-size vs primacy:

• India's spread of large cities (no national primate city) reflects federal, many-centred growth.

• Primacy at the state level, as with Kolkata in West Bengal, shows uneven regional growth with colonial roots.

• Central place theory in planning:

• It helps decide where to place market towns, haats, schools and hospitals at each level.

• It can guide where to put rural growth centres and how to plan services under the Degree of Urbanisation approach [2].

• Megalopolis formation in Delhi–NCR and Mumbai–Pune:

• It needs planning across state borders (regional planning boards).
• It needs transport corridors and better air and water management, because metro regions are merging faster than city limits are redrawn.