What is a "Gamma City" according to the Globalization and World Cities Research Network (GaWC)?

The Globalization and World Cities Research Network (GaWC) is a think tank that studies the relationships between world cities in the context of globalization. The GaWC examines cities worldwide to narrow them down to a roster of world cities, then ranks these based on their connectivity through four "advanced producer services": accountancy, advertising, banking/finance, and law.

The roster is sorted into categories of Alpha world cities (with four sub-categories), Beta world cities (three sub-categories), Gamma world cities (three sub-categories), and additional cities with High sufficiency or Sufficiency presence.

Gamma level cities are cities that link smaller economic regions into the world economy and are classified into three sections, Gamma +, Gamma, and Gamma − cities.