diff --git a/iTunesParser.py b/iTunesParser.py
index b9da926..efb5d09 100644
--- a/iTunesParser.py
+++ b/iTunesParser.py
@@ -136,19 +136,22 @@ class ITunesParser:
         # Add artist
         if akey not in self._artists:
             self._artists[akey] = {
-                'id': len(self._artists),
+                'id': len(self._artists), # TODO Calc an uniq ID (permit to replace data)
                 'name': akey,
                 'count': 0, 'plays': 0, 'rating': 0,
+                # TODO Use Rating with R upper case to be coherent with iTunes data
                 'genres': set()
                 }
 
         # Compute information
-        rating = (track['Rating'] // 20) if 'Rating' in track else 0
-        # TODO Improve rating that currently can go ahead to 100
+        rating = track['Rating'] if 'Rating' in track else 0
+        # TODO If no Rating, don't take 0
         plays = track['Play Count'] if 'Play Count' in track else 0
 
+        rating = self._calc_rating(rating, self._artists[akey]['rating'], self._artists[akey]['count'])
+
         self._artists[akey]['count'] += 1
-        self._artists[akey]['rating'] += rating
+        self._artists[akey]['rating'] = rating
         self._artists[akey]['plays'] += plays
 
         if 'Genre' not in track:
@@ -172,18 +175,22 @@ class ITunesParser:
             self._albums[akey] = {
                 'id': len(self._albums),
                 'name': akey,
-                'count': 0, 'plays': 0, 'rating': 0,
+                'count': 0, 'plays': 0, 'rating': 0, 
+                # TODO Use Rating with R upper case to be coherent with iTunes data
                 'genres': set(),
                 'artist': set()
             }
 
         # Compute information
-        rating = (track['Rating'] // 20) if 'Rating' in track else 0
+        rating = track['Rating'] if 'Rating' in track else 0
+        # TODO Use Album Rating
+        # TODO If no Rating, don't take 0
         plays = track['Play Count'] if 'Play Count' in track else 0
 
+        rating = self._calc_rating(rating, self._albums[akey]['rating'], self._albums[akey]['count'])
+
         self._albums[akey]['count'] += 1
-        self._albums[akey]['rating'] += rating
-        # TODO Improve rating that currently can go ahead to 100
+        self._albums[akey]['rating'] = rating
         self._albums[akey]['plays'] += plays
 
         if 'Genre' not in track:
@@ -231,6 +238,9 @@ class ITunesParser:
             file_albums.write(bytes("\n", 'UTF-8'))
         file_albums.close()
 
+    def _calc_rating(self, added_value, current_rating, count):
+        return (current_rating * count + added_value) // (count + 1)
+
 #### main block ####
 
 # Default input & output files