Rotten Tomatoes and Selection Bias

The AVI sent along a link (from 2013) this week about movies that audiences love and critics hated as judged by their Rotten Tomatoes scores.

For those of you not familiar with Rotten Tomatoes, it’s a site that aggregates movie reviews so you can see overall what percentage of critics liked a movie. After a few years of that, they also allowed users to leave reviews so you can see what percentage of audience members liked a movie. This article pulled out every movie with a critic score and an audience score in their database and figured out which ones were most discordant. The top movies audiences loved/critics hated are here:

The most loved by critics/hated by audiences ones are here:

The article doesn’t offer a lot of commentary on these numbers, but I was struck by how much selection bias goes in to these numbers. While movie critics are often (probably fairly) accused of favoring “art pieces” or “movies with a message” over blockbuster entertainment, I think there’s some skewing of audience reviews as well. Critic and audience scores are interesting because critics are basically assigned to everything, and are supposed to write their reviews with the general public in mind. Audience members select movies they are already interested in seeing, and then review them based solely on personal feelings.

For example, my most perfect movie going experience ever was seeing “Dude, Where’s my Car?” in the theater. I was in college when it came out, and had just finished some grueling final exams. My brain was toast. A friend suggested we go, and the theater was full of other college students who had also just finished their exams. It was a dumb movie, a complete stoner comedy from the early 2000s. We all laughed uproariously. I have very fond memories of this, and the movie in general. It was a great movie for a certain moment in my life, but I would probably never recommend it to anyone. It has a 17% critic score on Rotten Tomatoes, and a 47% audience score. This seems very right to me. No one walks in to a movie with that title thinking they are about to see something highbrow, and critics were almost certainly not the target audience. Had more of the population been forced to go to that movie as part of their employment, the audience score would almost certainly dip. If only the critics who wanted to see it went, their score would go up.

This is key with lists like this, especially when we’re looking at movies that came out before the site that existed. Rotten Tomatoes started in 1998, but a quick look at the top 20 users loved/audiences shows that the top 3 most discordant movies all came out prior to that year. So essentially the user scores are all from people who cared enough about the movie to go in and rank it years after the fact.

For the critics loved/users hated movies, the top one came out in 1974. I was confused about the second one (Bad Biology, a sex/horror movie that came out in 2008), but noted that Rotten Tomatoes no long assigns it a critic score. My suspicion is that “100%” might have been one review. From there, numbers 3-7 are all pre 1998 films. In the early days of Rotten Tomatoes you could sort movies by critic score, so I suspect some people decided to watch those movies based on the good critic score and got disappointed. Who knows.

It’s interesting to think about all of this an how websites can improve their counts. Rotten Tomatoes recently had to stop allowing users to rate movies before they came out as they found too many people were using it to try to tank movies they didn’t like. I wonder if sending emails to users asking them to rank (or say “I haven’t seen this”) to 10 random movies on a regular basis might help lower the bias in the audience score. I’m not sure, but as we crowd source more and more of our rankings, bias prevention efforts may have to get a little more targeted. Interesting to think about.

 

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