Some nations have regulations limiting the squad selections in various ways, such as total number of foreign players or a minimum number of "home-grown" players. In Serie A and La Liga I believe there are limitations on number of non-EU citizens. In England, foreign players need to get work permit, which I believe requires the team to justify "employing" that particular player.
One usually claims that these regulations exist to enforce the teams to invest in youth academies and that the national teams do better in the long run. My question is whether or not this is claim can be backed up by statistics, in other words whether or not these regulations actually help develop national football.
I, personally suspect that it's not as beneficial as one might think, or hope. Isolating the league from foreign talent will likely give first team exposure to players from that nation, but without having to compete for the position, the players will ultimately not push themselves as hard as one would expect. Of course I can not back this up with statistics or literature, thus I ask this question.