The map is meant to show relative GDP per capita. Tokyo is very dense, and has an extreme GDP per capita compared to most other comparatively dense cities in C

The map is meant to show relative GDP per capita. Tokyo is very dense, and has an extreme GDP per capita compared to most other comparatively dense cities in China. Your man in an oil field is not part of this exercise, except where of course, he is. But if you know your intra-China geography, the "oil fields" are pretty obvious.