The graph below describes the composition of the major European football leagues by nationality groupings for the 2015-2016 season.
A clear picture emerges again. The Premier League has the lowest percentage of domestic (national) footballers and also the (joint) lowest percentage of footballers from outside of the EU (Non EU). As you can see from the graph, the Premier League attracts talent from other EU countries like no other major European league. In particular, the Premier League attracts talent from the surrounding region - the Irish, Scots and Welsh flock to the Premier League and are rarely seen elsewhere. The other major European leagues attract far fewer regional players.
La Liga has the highest percentage of domestic (national) players out of the big 5 this season. Lique 1 attracts the highest percentage of non-EU talent, the majority of which is sourced from Western Africa and South America.