"InnocousFox - I beg to differ. I highly doube that the Chicago O&D traffic is a "very small percentage of what goes through ORD
Chicago is the third biggest city in the country (not to mention home to many Fortune 500 companies) do you think everyone flies out of MKE
You are displaying either a lack of understanding of how a hub works or a simple inability to grasp the mathematics involved.
Chicago O&D = All pax between Chicago and all Feeders = 1 to N
Other O&D = All pax between any Feeder and all other Feeders = N to N
Even if no N is bigger than Chicago, if there are 200 Ns the total O&D between any N to any of the other 199 Ns is likely to be larger than the Ns to Chicago alone.