Is it people without health insurance?
too bad there are so many countries without a color
Yeah, I thought that might make it too difficult. I don't think the thing in question is even considered in most countries though and in some of the poorer countries it may just arbitrarily be present.
So a choice for some countries and something that just happens in others. Sounds like something naturally occurring in some places that is artificially induced in others, in a somewhat random way.
Has to do with health care, but not directly.
Population drinking water with fluoride in it?
You got it.
Did I give away too many clues or are you just smart?