So, when Bill Gates walks into a bar, on average, the 10 regular people in it are all billionaires, and if I asked the, could easily throw a million my way.
If you are going to look at incomes, median is a better measure, and one should, as noted above, consider how that wealth and income are concentrated.
http://en.wikipedia.org/wiki/Gini_coefficient
http://en.wikipedia.org/wiki/List_of...ni_coefficient
Let me know when this guy submits his research to an economics journal.