I'm not sure what their formula is. Their numbers are based on the assumption that there are 6 billion people on earth. Not sure what they mean when they say that the average income worldwide is $5,000 a year. Seems kind of high to me.
Anyway, check it out. It'll give you some perspective. Maybe those two extra hazelnut lattés a week don't really matter, in the grand scheme of things?
Ah, heck! Who am I kidding? Of course, they do!