I just looked through quickly, but it appeared that the segment with the most companies in the list is insurance... I guess Warren Buffet is still right...
When you account for total revenues by sector it's the commodities trading business which comes out ahead though.
Just adding up Vitol, Transfigura, Cargill and Koch Industries you get to 665B in revenues.
Commodities trading is a behemoth, everything that surrounds us had to be mined and refined at some point, and most of it comes from very far, way beyond a 10-mile radius, thus prompting the need to move commodities around.
