According to the United Nations data file there are 195 countries which meet the criteria of a country. There are 94 countires affiliated with the IRB (union code) Therefore as close as can be calculated 48.20% of the world are involved in the game
Rugby Players
15 players in a rugby team
Rugby Players' Association was created in 1998.
for rugby league it is 13 players and for rugby union it is 15 players
There are 122,598 registered rugby union players in japan.
Sadly there are no viable statistics to be able to respond with any accuracy at all for this question
Rugby League has 13 players on each team. Rugby Union has 15 players on each team. There is a recognised game of seven-a-side in Rugby Union.
Rugby Union 15 players, (8 forwards and 7 backs) (Rugby League 13 players)
There are lots but they are all keeping quiet about it, certainly the famous ones are.
Rugby players
Welsh Rugby Players Association was created in 2003.
Rugby Union Players Association was created in 1995.