Which productive resources can be a source of income when exported?

"social stratification refers to the way people are ranked and ordered in society. in western societies, stratification is primarily seen and understood as a result of socioeconomic status, which produces a hierarchy in which access to resources, and possession of them, increases from the lower to the upper strata"

all cities have a governor

all cities are in states or provnies then country

all cities have people

difference

some are rich

some are poor

some are average