Netflix’s star ratings were personalized, and had been from the start. That means when you saw a movie on Netflix rated 4 stars, that didn’t mean the average of all ratings was 4 stars. Instead, it meant that Netflix thought you’d rate the movie 4 stars, based on your habits (and other people's ratings). But many people didn’t get that.
“That’s not the way people are used to using star ratings on e-commerce ratings” Johnson said. Take Amazon, for instance. “In those contexts, those star ratings are an average.” People assumed Netflix was the same.
This was a problem because people weren’t as motivated to rate titles when they thought they were just a drop in the bucket of all Netflix reviews. They didn’t understand that the more they rated, the better the system would be at understanding their tastes. “People don't intuitively think about it that way,” Johnson said.
So when looking for a replacement, Netflix wanted to make sure that was clear. That’s why Netflix settled on “thumbs up/down," which is widely understood to imply that you are training an algorithm to know what you like, Johnson said.