Have a look into this ESPN article (http://www.espn.com/nba/story/_/id/11744634/explaining-gravity-basketball http://www.espn.com/nba/story/_/id/11744634/explai

Have a look into this ESPN article (http://www.espn.com/nba/story/_/id/11744634/explaining-gravity-basketball http://www.espn.com/nba/story/_/id/11744634/explaining-gravi...), it touches on the determining factors and how it's quantified.