We have been blogging a lot about “bayesian voting” lately. In our previous post, however, we mentioned as an aside Netflix’s decision to replace its five-star cardinal voting system with a more simple binary system: thumbs up or thumbs down. Here, I want to call a time out to identify a problem with the binary system: what happens when two people are “Netflixing and chilling” and one person likes the movie and the other does not? Under the previous system, the viewers (husband & wife; boyfriend & girlfriend; friends; etc.) could compromise by assigning an average score–three stars out of five, say. Under Netflix’s binary system, by contrast, there is no fair way of aggregating the preferences of two people who diasagree about the quality of a movie. To the extent most people don’t watch movies alone, our objection should worry Netflix. Furthermore, even when one is watching a movie on Netflix alone, the binary system results in a loss of information, since it does not allow one to express the intensity of one’s like or dislike of a particular movie.
Note: Although YouTube and Rotten Tomatoes also employ simple binary votings systems, those websites at least disclose the ratio of likes to dislikes as well as (in the case of YouTube) the total number of views, which allows us to deduce the number of abstentions. In this respect, Facebook’s system of unitary voting (you can’t vote to dislike something) provides even less useful information than Netflix’s binary voting system.