http://www.whoscored.com/Regions/252/Tournaments/2/Seasons/5826/Stages/12496/TeamStatistics/England-Premier-League-2015-2016
This suggests we concede 12 shots per game, and we have conceded 24 goals in 20 games. In comparison, Liverpool have conceded the same number of goals, but from fewer shots per game.
I'm more concerned about the fact we don't convert our chances - for instance Leicester have fewer shots per game, but have scores 11 more goals.