How playing numbers can go from, say, 100 players under 10 years of age to maybe a third of that by the time teenagers leave school is a real issue for sports right across the globe.
New Zealand Rugby is fully aware of it and its implications and is trying to come up with ways to combat the drift away from sport in the teenage years.
That is where former Otago Country No8 and Pirates captain Warren Kearney comes in.
Kearney (31) has a role as the Central Otago youth rugby co-ordinator, employed by the Otago Rugby Football Union, and is trying to spread the word of rugby throughout Central Otago.
The union won some contestable funds from New Zealand Rugby and Kearney has been teaching rugby and its skills to children of all ages to keep them playing the game.
He is based in and around Central Otago, as it is a good test case for the rest of the country, he said.
The area had experienced real growth in junior numbers but that had not worked its way through to secondary school grades.
''In the last five years in places like Wanaka and Queenstown, we've seen a real growth in the younger grades; the number of under-7 teams has really grown,'' Kearney said.
''Other clubs around the area are also holding their own, if not increasing their numbers. But the secondary school teams have stayed mainly static. The question now is how do we keep them in the game, keep them interested, reducing the number of kids who are slipping through the gaps?''
Kearney said there were so many more options for teenagers and that was even more so in Central Otago, where the ski fields and adventure racing provided a real alternative for many young people.
To try to keep high school pupils involved in the sport and make it fun, Kearney was engaging with schools and playing different forms of games.
''We are looking at versions of the games so kids remain interested, and trying to get into secondary schools. Something we have been doing is a form of a quick rip where players rip a tag which is round their bodies.
''It is like rippa rugby but we still have the scrums and the lineouts. So you still have the core dynamics of the game. It is a 20-minute game, in four quarters, so it is a short, sharp sort of game but still with the rugby essence of it.''
Kearney said rugby was still very popular and was New Zealand's No1 sport, especially in country areas.
But that did not mean the game could rest on its laurels and it had to change as society changed.
Kearney has also started a player development group for players to learn more about things such as nutrition and conditioning.
He said the group would be a chance for players to improve their skills and abilities without having to go to a city.