Saudi Arabia is a third world country, yet rich as can be. Its an outdated model. The model was for countries not cities.Most off China is true third world. Only the major cities have risen above that.
A third world country would be a country in the late 1940 that was not aligned with Allied (first world) or communist (second world) countries.
Utilising today definitions of a third world country the most prevalent factors is the lack of a middle class and an ever growing debt ratio.
Sound familiar?