According to this ^, it's an average of 2.3 places worse but if you get to the quarter finals or better, it's 2.7 places worse the season you're in the Europa.
Particularly bad if you are Norwich or Ipswich.
No ill effects if you are Arsenal, Chelsea, Man U or, surprisingly, Millwall.
http://www.manchestereveningnews.co.uk/sport/football/football-news/stats-focus-europa-league-hinder-6723023
According to this ^, it's an average of 2.3 places worse but if you get to the quarter finals or better, it's 2.7 places worse the season you're in the Europa.
Particularly bad if you are Norwich or Ipswich.
No ill effects if you are Arsenal, Chelsea, Man U or, surprisingly, Millwall.