Chelsea and Arsenal's staggering youth sales profit vs Man Utd and 30 richest footballing giants

In modern football, the importance of a club's youth academy set-up is not only to build a senior team in seasons to come but to cash in on young talent to free up transfer spending money, a technique Premier League sides such as Chelsea and Tottenham Hotspur have used well.

That's according to the 446th CIES Football Observatory Weekly Post which has published a list of the 100 football clubs that boast the most profitable academies in the world. The study looks into revenues generated over the last 10 years but the transfer of players who spent at least three seasons at the outfit between the ages of 15 and 21.

Here's how Chelsea, Arsenal and Manchester United rank among other Premier League clubs and footballing giants from across the globe.