On my selection in December last year, there were 11 candidates.
Of the 4 who have made it, 1 SA, 1 UK, 1 USA, 1 Austrian.
I did not see any overt discrimination against any of the guys, there were 3 North Americans, 2 Iranians, 1 UK, 1 Brazilian, 1 Austrian, 1 Nordic fellow, 1 SA and 1 German.
The main requirements appeared to be an ability to get on with the other candidates in a pressure cooker environment, and know how to use the local taxis very early in the morning!