Equally Shed, if you're going to introduce airlines that only operate from MAN, then you have to include those only operating from LHR.
T&N: This may surprise you, but for once I completely agree with you. If you're going to conduct a statistical exercise, then you must include
all the data affecting both subject airports to yield meaningful results.
Skipness may do better to stick with the raw passenger stats per route or such like. Or even compare total long-haul pax per airport. But again, this only proves that LHR has a far stronger long-haul market than MAN which nobody here is disputing. What is the point of even arguing over this?