IMDb’s private voting system
In class we learned about voting and Arrow’s theorem. Majority Rule works well when there are two alternatives. However, we learned that in Arrow’s theorem, there is no voting system that satisfies unanimity and independence of irrelevant alternatives where there are more than two alternatives, except for dictatorship.
IMDb calls themselves “the world’s most popular and authoritative source for movie, TV and celebrity content.”
People may be familiar with IMDb’s top 250 movies and top 250 tv shows pages or individual movie pages with rating out of 10.
Their FAQ has a few questions that are funny and reveal how much people care about the accuracy of the rating of the movies on the website.
Example FAQ’s that made me laugh are:
“This is unfair! That film / show has received awards, great reviews, commendations and deserves a much higher vote! Can you change it to reflect this?
But film / show XYZ was never shown outside the US and yet you show a dozen votes from non-US users. Clearly they are fake votes and they should be deleted?
I know for a fact that the people who voted on a certain film cannot possibly have seen it! They have a grudge against the filmmakers. Will you delete/disregard their votes?”
IMDb says that they do not reveal how they calculate the weighted vote averages. Their decision to keep their formula for calculating an individual movie’s rating private may be explained by what we learned in class.
We learned that voting systems are easily manipulated. IMDb says “We will not disclose exactly if/when/how certain votes are weighted differently because the idea is, among other things, to give a more objective rating and neutralize attempts to artificially inflate or deflate the average user rating on a film or show.”
Perhaps in our last class on Friday we will learn about the best way to minimize manipulation in voting systems. Maybe we can understand methods that IMDb may use to more accurately aggregate millions of votes from users all over the world for individual movies.
http://www.imdb.com/help/show_leaf?votestopfaq
http://www.imdb.com/help/show_leaf?votes