Half Stars Considered Harmful

Fascinating and surprising (at least to me) observation on the Netflix Community Blog about user demand for half-star movie ratings:

So here’s what I learned from months of testing this across the country: when we make the ½ star options possible, we get fewer ratings. Significantly fewer ratings. We have argued these results internally for some time, and our best guess is that the complexity of doubling the number of choices from 5 to 10 deters many people from rating, so they just give up. (“3 stars? No, 3 ½ stars.. no… 3 stars… no… oh forget it…”)

4 comments

  1. James Grimmelmann Aug 7

    Exactly right. This is why I don’t use half-stars when I review stuff on my blog. Five tiers is about the human limit of reliable subjective ranking. If you buy the theory, it could explain a lot. For example, colleges used to have five grades, called A, B, C, D, and F. Now they have the same five grades, only they’re called A+, A, A-, B+, and B.

  2. Jamie Aug 7

    Time Out NY rates the restaurants it covers with between 1 and 6 stars. I really don’t get that. The 4-star system from the NY Times makes much more sense. Actually in reality it’s a 5-star system, because it’s possible for a restaurant to get 0 stars (poor to satisfactory). I also like the idea that even getting one star means the restaurant is at least “good.”

    Lastly, Adam, are you turning this blog into a Netflix blog? That would be cool.

  3. Adam Aug 8

    My problem is I have too many degrees of “liked it.” I can usually filter out films I don’t like in advance. I’d like to have greater stratification within the realm of films I do like. I suppose I could just make 2-5 stars be all varying degrees of “liked it,” but the system generally expects anything less than 3 to be “didn’t like it.”

  4. UG Aug 9

    Two entries about Netflix…now I’m not reading either!

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