And on the reasons for personal behaviour, you then add the "comfort" factor which is directly proportional to the length of the flight and is demonstrated by a greater desire for more space (ie upgrade to J or F).

Next factor is tolerance to discomfort - demonstrated by age (the older you get, the more quickly the "comfort factor" kicks in). Solved by avoiding kids, avoiding Y, avoiding Virgin, paying for better seat pitch and so on.

I'm sure a maths genius could make an equation out of this, but they are probably already working in "yield management".