How much, exactly, do the GDSs earn from distribution? It is a question that vexes airlines and other travel suppliers and has become under particular focus because of Lufthansa's decision to charge fees for bookings that use the global distribution systems as their channel.
The answer is a significant sum, particularly if you are Amadeus.
The chart below shows the geographic split of revenue made through the Amadeus GDS.
The location is defined as the location of the travel agency where a booking is made or the location of the airline receiving services.

Western Europe, the home of its former airline owners, accounts for by far the largest share of its revenues.
Amadeus generates almost €2.5 billion in revenues from its distribution businesses and the figure has been growing by around 5 to 6% for the past few years. The company has been growing market share though and total air bookings were up by 4.6% from 2013 to 2014, which accounts for some of this revenue growth.
It is, naturally, keen to protect its income streams. Distribution accounts for some 44% of revenues at the company, with travel IT services such as providing reservations and inventory management systems making up the remainder.