I have 8 players on my list that have reached the maximum XP ( 2,147,483,647).

How does the game rank them? The order appears to change from time to time. In checking with other players it seems our lists are not the same.

Example: my list has player 1 first, player 2 second and player 3 third. Her list has Player 2 first, then player 3 then player 1.

Is it completely random or is there an activity that effects the ranking?