Very interesting post! In my experience with my city, I find I hover between a 70-75 percent ratio with regard to population and income. I’ll have to take a look at the cities that do double the income compared to population.

As for the cities with 0 SIM incomes, they seem to have gone for a large population with no corresponding income producing cards. They have a large unemployed population. This wipes out their SIM income plus tends to receive funds from the government tax. Or, at least, this seems to me to be the case.