How are we to measure the weighted success of a manufacturer? We often do it by frames, but that is not particularly legitimate. Airbus could sell 3 A318s, while Boeing could sell 1 747-8. On number of frames, Airbus looks to be the winner, when the value of selling a 747-8 clearly exceeds the value of selling 3 A318s, no insult to the Babybus intended. We could do it by the monetary value of the sales. This has more validity and is appropriate for certain situations where we are thinking fiscally. Of course, it there are other situations where that would not reflect success. For example, the A340-600 is much cheaper than the 777-300ER, but in terms of capacity, they are equal. So Boeing could sell fewer 777-300ERs than Airbus A340-600s, but still come out on top.
What we need is to take into account the capacity of the aircraft. Pax capacity is a bad measure because it is too variable and obviously doesn't include freighters. So the solution is obvious: MTOW. To judge the normalised order book of a manufacturer, we simply add up the MTOW of the frames sold. So we say Boeing or Airbus have sold so many kilograms of payload this year.