I agree — in general, wealth is a better indicator of how rich a person is. Lost somewhere among my too many footnotes you can find this: “Credit Suisse, for example, calculates that you need net assets of $93,170 to be among the world’s wealthiest 10%, and $871,320 to be among the top 1%.”

The reason I chose to use income in the post is because it makes comparisons with other definitions easier. It so happens that both extreme poverty and the middle class are generally defined in terms of income rather than wealth.