The Rank Size Rule is a theory of how large the population of the different major cities are in a country should be. The Rank Size Rule, inspired by Zipf’s Law Applied to Distribution of Cities (1935), says if all cities in a country are placed in order from the largest to the smallest, each one will have a population 1/nth the size of the largest city in the country.
Largest City in a Country - Population of 1,000,000
1,000,000 / 1
2nd Largest City in a Country - Population of 500,000
1,000,000 / 2
3rd Largest City in a Country - Population of 333,333
1,000,000 / 3
4th Largest City in a Country - Population of 250,000
1,000,000 / 4
5th Largest City in a Country - Population of 200,000
1,000,000 / 5
Some countries have some cities that fit in the rank size rule but other cities populations in the top 10.
In the United States, New York City is largest, then Los Angeles, then Chicago, then Houston, then Phoenix, then Philadelphia, etc.
In the USA, the top 5 cities fit in the Rank Size Rule, but cities 6-10 do NOT.
Some countries have a largest city that is way more than 2x the size of the 2nd largest city.
Countries that have this exception generally have Primate Cities.
Often, because of real life, theory doesn’t always match up with reality. In many countries, the largest city in the country is a primate city. This means that the largest city will have a population of over 2x of the 2nd Largest City in the Country. The primate city is usually far more populated and far more economically important. The largest city, when a primate city, has the largest influence in the country.
Paris, which has a population of 9.6 million is the largest city and most economically important city of France, while Marseilles has a population of 1.3 million. This makes Paris a Primate City.
The chart below describes the advantages and disadvantages of a Primate City!
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6.4The Size and Distribution of Cities