From which country are the vast majority of 10-goal handicapped polo players?

The players are rated on a scale from minus-2 to 10. Minus-2 indicates a novice player, while a player rated at 10 goals has the highest handicap possible. It is so difficult to attain a 10-goal handicap that there are fewer than two dozen in the world, and about two-thirds of all players handicapped are rated at two goals or less. Currently, most living ten-goal players are Argentine, with few exceptions.