How much money are brokers really making from owner-operators' hauls?

“When looking at margin percentages by equipment type," according to the published paper, "flatbed (F) comes in on top with a mean margin of 15.14%, followed by refrigerated (R) at 13.82%, with dry van (V) at the lowest margin" at 13.01%. The mean (average) margin reported among all the loads in the sample was 13.47%