The Definitions of Region-level and City-level

Based of this information provided I would suggest the following:

  • Regional Census = Provincial-level divisions
  • City Census = Municipal-level divisions

I assume the that Provincial-level divisions (provinces, special autonomous provinces, special cities, metropolitan cities and special autonomous cities) are all mutually exclusive and have no overlap. E.g. a special city is not within a province. I suspect this may not be the case.

I’d go with what culturally makes sense. Ask your friends which census they’d expect to find Busan, Ansan, Seoul or Sejong in - Regional or City.