4 Driver has hit the nail on the head. There are many, many based FO's (into 3 figures I hear) who will stay on their bases where their children are settled at School and Mrs FO has no intention of moving from nice house to a sh*thole in the smog. Where else in the world do you have to upsticks and move half way around the world just to get a perfectly normal promotion?
As I've said before, this is the ticking time bomb along with recruiting people on rubbish terms who will leave and get a proper job elsewhere. Well done Cathay - very smart and forward thinking.