@ North West
The International/International transfer PAX add nothing to the local economy through tax or spending locally, but the point is that without them it would mean that many routes are unviable because they wouldnt have enough PAX to make it economical. This is the basic premise on which a hub works, and is the key difference between London having a lack of runway capacity (which it doesn't) to a lack of hub capacity (which it does!)
The reason they add to the economy is that, with a far greater choice of flights to be able to sustain, means that many more companies will do business here, tourists from far and wide will be able to visit easily and international students can come to study here with direct flights back to their home cities. This is hugely beneficial to the economy as a whole, with estimates varying at somewhere around the UK losing £13bn a year in lost business due to LHR's capacity issues (though this is, by definition, very difficult to accurately state!)
In summary, that is why the middle east is investing so heavily in hub airports, and why AMS, CDG and FRA are so keen to retain their status.
Last edited by Libertine Winno; 3rd Apr 2013 at 09:51.