Wine scoring is an attempt to objectify a wine’s performance relative to a theoretical ideal. UC Davis came up the 20 point scale where a wine is granted or denied points for appearance (color & calrity), perceived balance of sugar and acidity, aroma, taste, and overall quality with 20 being a perfect score. Robert Parker of the Wine Advocate uses a 100 point scale, which is a gimmick since he assigned every wine 50 points to begin with. 49 points is equal to zero and a grade of 90 really meant it earned only 40 points (1). But 90 points sounds more impressive and it correlates to our upbringing in school and to our personal ideals of 100 as a perfect score.
(1) Inventing Wine, by Paul Lukacs