I started off by gathering ratings from IMDB (User/Critic Average), Rotten Tomatoes (Tomatometer, Critic Average, Audience Score, User Average), Metacritic (Critic Average, User Average) and Letterboxd (User Average). I was then able to determine a rating (out of 10) for each individual rating and therefore come up with an average rating for each site. Each site’s average rating was then weighted fairly so that no site’s ratings were favored above the rest.
The next step was to make sure that each film was treated fairly. Other top movie list’s like IMDb’s Top 1000 removes films that have under a certain viewing number (25,000 I think), but rather than ruling out films that may have been overlooked by the general audience (especially older films), I opted to alter these films score by carefully deducting points depending on how many people have seen it, and therefore voted on it. I also thought it was needed to make sure that recent films (released within the past 36 months) were also not favored, as it usually takes 3 years for the average rating to settle down. So I also added a deduction to these films that fell under this rule.
Taken from here: https://www.reddit.com/r/movies/comments/3hbiio/update_1001_greatest_movies_of_all_time_plus/
