The environmentalist in me is thinking a single billionaire's carbon impact is probably lower than a 1,000 millionaire's carbon impact. A single billionaire (say Warren Buffet) has a consumption of probably $200,000 a year with the remainder held in investments. A 1,000 millionaire's consumption is probably also $100,000 a year, with the remainder held in investments. So the 1,000 millionaires have basically about 500x the environmental impact than a single billionaire.