CIES collated data from across Europe’s ‘big five’ leagues - the English Premier, League, Spanish LaLiga, German Bundesliga, Italian Serie A and French Ligue 1 - to look at where players had been developed.
The Uefa definition of a 'club-trained' player is for the player in question to have been at the club for at least three seasons between the ages of 15-21 years old.
Across Europe's top five divisions, Real Madrid are the clear frontrunners with 43 players fitting into that category - well above next-best Barcelona (32).
Man United sit ninth on the list with 24 players, though Arsenal (23) are just one behind and a little ahead of Chelsea (20).
Of Europe's top 31 divisions, FK Partizan have produced a huge 85 players currently plying their trade across the continent, with Ajax (77) unsurprisingly not far behind.