Depends where they come from. SA and Canadians never leave becasue they have never had it so good. Brits, Aus, and US hang around until something better comes along. 3rd world you will never get to leave not only for the airline but for the country as well.
"Captain" ED said 4% leaving a year is perfectly acceptable and EK probably has been getting that for the last 3 years. V Aus is going to scew those numbers in the months to come though.