The Settlement Hierarchy: From Hamlets to Megacities

The settlement hierarchy is the ranking of settlements by size and function, from the smallest, such as isolated dwellings and hamlets, through villages, towns and cities, up to conurbations and megacities, with larger settlements offering more and higher-order services to a wider area. In brief: a hamlet has a few houses and no services, a village has a few basic services, a town has shops, schools and a market, a city has a wide range including a cathedral or university and specialist hospital, and a megacity is a city of more than 10 million people. Two ideas explain the pattern: the threshold population needed to support a service and the range that people will travel to use it.

The hierarchy shows how services are distributed and why people travel to larger centers for some goods. This guide explains the levels of the hierarchy, the ideas of threshold and range, central place theory, compares the settlement types in a table, works through an example, outlines the history of the theory and corrects common mistakes.

What are the levels of the settlement hierarchy?

• Isolated dwelling and hamlet: a single farm or a very small group of houses, typically without shops or services.
• Village: from a few hundred to a few thousand people, with a few services such as a primary school, pub, church and perhaps a small shop.
• Town: several thousand to tens of thousands of people, with a market, supermarkets, a secondary school, a health center and some industry or offices.
• City: a large settlement with a wide range of services, such as a university, a major hospital, department stores, theaters, a cathedral and regional government. In some countries, the term is a legal title.
• Conurbation: a continuous urban area formed when cities and towns grow together, as in the Ruhr in Germany or Greater Manchester.
• Megacity: a city with more than 10 million inhabitants, for example Tokyo, Delhi, Shanghai, São Paulo, Mexico City and Cairo. The UN counts more than 30 of them, and the number is rising, especially in Asia.

The exact population limits differ between countries, so the categories are better understood as a ranking than as fixed numbers. As the hierarchy rises, the number of settlements at each level decreases: there are many villages, fewer towns and very few big cities.

What are threshold, range and order of goods?

The threshold population is the minimum number of customers needed to support a service. A newsagent may need a few thousand people, a department store tens of thousands and a specialist hospital hundreds of thousands. The range is the maximum distance people are willing to travel to use a service. Goods that people buy often and cheaply, such as bread and milk, are low-order (convenience) goods with a small threshold and range. Goods bought rarely and at greater cost, such as furniture, jewelry or specialist medical care, are high-order (comparison) goods with a large threshold and range, and they are found only in larger settlements. The area served by a settlement is its sphere of influence or hinterland.

What is central place theory?

Walter Christaller, a German geographer, proposed central place theory in 1933 on the basis of a study of southern Germany. On a flat, uniform plain with evenly spread population, he argued that settlements would form a hierarchy in which each higher-order center serves a larger market area. Market areas are hexagonal, because hexagons cover the plain without gaps and are close to circles. In the simplest case (known as k = 3), every higher-order place serves itself and one third of each of six lower-order places, so each market area contains three areas of the next lower level. The model is a simplification that does not account for hills, rivers, transport routes and historical factors, but it helps to explain the typical pattern of many small places and few large ones.

What are megacities?

Megacities reflect rapid urbanization. Many are in lower- and middle-income countries, such as Dhaka, Lagos and Kinshasa. They offer jobs, but face challenges of housing, transport, pollution and inequality. Some large cities are also primate cities, which are much larger than the next city in the country and dominate its economy, such as Bangkok. Others are world cities, which are important centers of finance and decision-making.

Settlement types compared

Worked example: threshold and range

1. Number of customers: a bakery needs 3,000 customers (its threshold). A village of 1,200 people cannot support it on its own, but a town of 9,000 can.
2. Customers in range: if people are willing to travel 5 km to a supermarket, its market area is a circle with a radius of 5 km: π × 5² = 78.5 km². With a population density of 150 people per km², there are 78.5 × 150 = 11,775 potential customers.
3. Viability: if the supermarket needs 10,000 customers, it is viable, since 11,775 is greater than 10,000. At a density of 100 per km², the area holds 7,850 people, so it would not be viable at this range.
4. Higher-order good: a specialist shop with a threshold of 50,000 and a density of 150 per km² needs an area of 50,000 ÷ 150 = 333 km², which is a radius of √(333 ÷ π) = about 10.3 km. Customers must travel farther, so only larger centers have it.
5. Hierarchy count (k = 3): if there is 1 city, the model gives 2 towns, 6 villages and 18 hamlets in the next levels (1, 2, 6, 18 and so on), with the numbers multiplying roughly by three at each lower level beyond the first step.

How did the theory develop?

Christaller’s work was published in 1933 and became widely known after the Second World War, when geographers and planners adopted it. August Lösch developed a related theory of market areas in 1940. Later studies tested the model in regions such as the American Midwest and parts of Europe, and found general support for a hierarchy but also many differences. The idea of a settlement hierarchy is still used in planning to decide where to place schools, hospitals and shopping centers. Online shopping and mobility have changed the thresholds and ranges of many services, so the traditional hierarchy of high streets is changing.

Which mistakes are common?

Mistake 1: Thinking that size is the only difference between levels

Settlements are ranked by both size and the range of services they offer.

Mistake 2: Confusing threshold and range

Threshold is the minimum number of customers. Range is the maximum distance customers will travel.

Mistake 3: Believing that the same population defines a town everywhere

The size at which a place counts as a village, town or city differs between countries and regions.

Mistake 4: Taking central place theory as a literal map

The theory assumes an even plain and equal transport in all directions. Real patterns are shaped by geography, history and trade routes.