[Excerpt] According to the popular press and media a common discussion point amongst customers of service industries is why one person is charged more than another for what is apparently the same service or product. Typical anecdotal questions include 'Why is the passenger in the next seat on an aeroplane paying less than half of the fare that I have been charged?' or 'Why is it costing me £70 to travel to London from Birmingham on the train when the passenger across the aisle has a ticket that cost only one quarter of this?' The answer to this perceived unfairness is usually due to Yield Management (YM), sometimes also called revenue optimisation.