Primate city

Primate cities are cities in a country that have far more people and influence than every other city in it. For it to be called a primate city, it must have more than two times as many people and two times as much influence (such as in the country's economy, resources, education, health care, etc.) than the country's second largest city. Countries with primate cities usually have a large inequality in its development, but richer countries as well as poorer countries can have primate cities.
An example of a rich country having a primate city is the United Kingdom, where its largest city London has more than 8 times as many people as its second largest city Birmingham.
Bangkok is one of the world's most primate city because its population is 9 times bigger than the second largest city in Thailand and 70% of the country's resources go to Bangkok.
The United States has never had a primate city on a national level due to the decentralized nature of the country, and because the second largest city of the country is not far behind in population and GDP. New York City, which is the largest city and the largest economy in the United States, is for this reason not a primate city of the country. The metropolitan area of New York City has 21 million residents and Los Angeles has 16 million residents. 
Sub-national divisions can also have primate cities. For instance, New York City is New York State's primate city because its population is 32 times bigger than the second largest city of that state. New York City has 44% of the population and has 65% of the GDP of New York State.