diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index 3546c7e7..e7dba16d 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -37,6 +37,11 @@ class Exercise < ActiveRecord::Base
     else 0 end
   end
 
+  def average_number_of_submissions
+    user_count = internal_users.distinct.count + external_users.distinct.count
+    return user_count == 0 ? 0 : submissions.count() / user_count.to_f()
+  end
+
   def average_working_time
     self.class.connection.execute("""
       SELECT avg(working_time) as average_time
diff --git a/app/views/execution_environments/statistics.html.slim b/app/views/execution_environments/statistics.html.slim
index 38112c4f..ae2bf4f8 100644
--- a/app/views/execution_environments/statistics.html.slim
+++ b/app/views/execution_environments/statistics.html.slim
@@ -11,5 +11,5 @@ h1 = @execution_environment
         tr
           td = exercise.title
           td = exercise.average_score
-          td = exercise.submissions.count()
+          td = exercise.average_number_of_submissions
           td = exercise.average_working_time