Previously, I had briefly touched upon players graduating from the Under-19 World Cup to the senior levels. Thanks to some fantastic research courtesy of
chrisps
, we have access to an in depth analysis at their transition rate. I can't speak highly enough about the work that went into putting this together.
https://chrispscricket.files.wordpress.com/2016/02/attainment-level-page-001-e1456090941346.jpg?w=899
The summary analysis of the 555 players shows that 45% have gone on to play international cricket (not all with the nation they represented at the Under 19 age group). 5% have not played any professional senior cricket.
At Test level, there is a heavy dependence on Under 19 World Cup graduates, with around one-half of the debutants in the years following tournaments having participated in the junior World Cup.
Unless from England or India, an Under 19 World Cup participant has close to, or better than, an evens chance of senior international cricket.
It is interesting to note that just 10% of players that have appeared in an Under-19 World Cup have gone on to play at least one ODI.
https://chrispscricket.files.wordpress.com/2016/02/u19-country-analysis-page-001-e1456091147146.jpg?w=899
There are some stark country-by-country differences. The youngsters of Bangladesh and Zimbabwe have had a higher likelihood of becoming full internationals, two-thirds in the latter case – perhaps reflecting that selection in those countries is from a smaller pool of players. On the other hand, barely one-quarter of those who have appeared at under 19 World Cups for England have played for the senior team. Unsurprisingly, England, with its 18 first class counties has had no players fail to reach the senior professional game – nor did Pakistan, South Africa and India.
I highly recommend reading the entire article:
chrispscricket.wordpress.com/2016/02/21/...-under-19-world-cup/ 
