Note that the size of the boxes isn't really the relevant metric, but rather the color (which indicates the likelihood of someone in the profession being part o

Note that the size of the boxes isn't really the relevant metric, but rather the color (which indicates the likelihood of someone in the profession being part of a household in the 1%). A darker color indicates a higher correlation between the profession and the income (ie, less likely that they simply married into wealth). Looking at the color, we see doctors, lawyers, and brokers, which is about what you'd expect. If the data set was narrowed further to the top 0.1%, you would probably see the fee-based professions drop off and the high-end brokers dominate. There are only so many hours to bill or patients to serve in a day, while there is no limit to the size of a transaction from which a broker can skim a percentage.