Note that one appearances in league football for each season were counted - appearances in FA Cup, League Cup, European, etc were disregarded
The number of Premier League players have steadily declined from 39 in 2009-10 to only 13 this season. There hasn't been an increase in player numbers season-to-season since 2011-12.
Championship numbers were almost double those in the Premier League in 2009-10 with 70 of the Boys in Green appearing in England's second tier. This has declined to 33 this season, with only slight increase in 2013-14, 2014-15, and 2016-17 arresting the slide.
Following the European Championships in 2012, there was a brief improvement in the player numbers in League One and League Two from the 2012-13 season until 2015-16 and declined since then, with the only increase coming in League One in 2017-18.
While there has been improvement in the fortunes at underage level for Ireland, this has not yet had an effect on the numbers playing at senior level in England, and it may be at least another 12 months before we start to see the talent from the underage sides make an impact for their respective club sides.
(mouse over the dots on the graph to see the players from that division that season)