Many people choose to move to or live in cities for various reasons. Cities offer a wide range of opportunities, amenities, and services that are not always available in rural areas. However, as a city grows larger, its growth may slow down once it reaches a certain size. This phenomenon can be explained by the Rank-Size Rule, which is a principle that describes the distribution of cities based on their rank and relative population size.
Understanding the Rank-Size Rule
The rank-size rule is a principle that states that the population of a city is inversely proportional to its rank. In other words, the second-largest city in a country will have half the population of the largest city, the third-largest city will have one-third the population, and so on. This rule is inspired by Zipf's Law, which reflects the inverse proportionality between things relative to their ranks.
Applying the Rank-Size Rule
The formula for the rank-size rule is 1/nth, where n represents the ranking of the city's population size. By knowing a city's rank, we can estimate its population size relative to the largest city in the country. While the rank-size rule is not always consistent across all countries, it is a useful tool for understanding the distribution of populations among cities.
Although the rank-size rule is commonly associated with cities, it can also be applied to other contexts. For example, the populations of countries can follow a pattern of exponential inverse regression based on their rank. While some countries, like China and India, may deviate from this pattern, most countries' populations align closely with the expected distribution according to the rank-size rule.
Implications of the Rank-Size Rule on Urban Development and Equity
The rank-size rule can provide insights into a country's level of development and inclusivity. It may indicate a more equitable distribution of power and wealth compared to other models. However, rapid growth, as seen in many Asian countries, can make it challenging to adhere to the rank-size rule, with power and investment concentrated in one city. This limits urbanization and development from spreading across the entire country.
The rank-size rule is more effective in countries with long histories of large urban populations, allowing for urbanization to expand over time.
Rank Size Rule vs Primate city
The rank-size rule signifies a hierarchy of progressively smaller but independently functional cities, while a primate city dominates as the largest city in a country, centralizing industry, power, and societal trends. A country with a single primate city, instead of a range of cities following the rank-size rule, may suggest lower resilience; the primate city could negatively impact the rest of the country, unlike in countries adhering to the rank-size rule where power and wealth are more evenly distributed.
Thailand serves as an example of a country with a primate city, Bangkok, significantly larger than other urban areas. Primate cities often reflect or exacerbate inequality, uneven development, and lack of equity. Provinces surrounding Bangkok may have significantly higher GDP per capita than rural provinces in Thailand.
Primate cities are common in developing countries experiencing rapid economic growth or those with histories of inequality and authoritarian rule concentrating wealth in the political center. However, authoritarian countries may also adhere to the rank-size rule.
Advantages and Disadvantages of the Rank Size Rule
There are several advantages to the rank-size rule. Countries that adhere to this principle tend to be more developed and have a rich history of urbanization. They also experience more balanced development and less inequality. By having a variety of large cities, a country can enhance its resilience and security, as resources and wealth are not concentrated in a single city.
Some weaknesses may be that there is no unified definition of where exactly a city should end and begin, almost making it possible to adjust city boundaries to fit the rule. Another weakness would be that it is a rough estimation of city sizes, and when dealing with large countries, this can mean that the measurement would be off by several hundred thousand people. Lastly, the rank-size rule is only sometimes applicable to some countries, as many countries have primate cities instead; therefore, it would be inaccurate to assume the size of other cities in any given country just because you know the rank and size of one city.
Rank Size Rule Summary
The Rank Size Rule offers a pattern of proportionality in urban geography, helping to describe how populations are distributed across cities. It highlights that the higher the rank of a city, the smaller its expected population. Although this rule is not a universal or precise measurement, it serves as one of several theories that elucidate population distribution patterns observed in many countries.