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Analysis of whether IMDB ratings suffer recency bias

72 pointsby eoinmurray92almost 6 years ago

16 comments

8innovatealmost 6 years ago
This is definitely not the &#x27;recency bias&#x27; I expected.<p>I&#x27;ve always noticed that when a show is released it gets WAY higher ratings in the first week or so of the release date. I&#x27;ve learned not to trust the ratings until at least a 2 weeks after a release.<p>It looks like this analysis focuses on the year a film was released. This seems like it would be a lot harder to determine because film quality changes (subjective) and the audience writing reviews is probably changing over time.
PaulHoulealmost 6 years ago
It&#x27;s well known that movie rankings do. This was key to the resolution of<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Netflix_Prize" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Netflix_Prize</a><p>The time series of reviews of movies like<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sucker_Punch_(2011_film)" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Sucker_Punch_(2011_film)</a><p>and<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Batman_v_Superman:_Dawn_of_Justice" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Batman_v_Superman:_Dawn_of_Jus...</a><p>tend to have many early bad reviews by mainstream people who can&#x27;t get past things that they find squicky and the lack of the usual &quot;Hollywood Happy Ending&quot; but that get better reviews from &quot;true fans&quot; later on who enjoy the fact that the directors tried to make something different even if it was flawed.
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minimaxiralmost 6 years ago
Recency bias came up a few days ago in a previous HN submission by the OP, and the OP also commented in: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20099023" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20099023</a><p>In that subthread, I posted a heat map data visualization I made of IMDB rating vs. release year, which is suspiciously similar to the one OP made: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20099344" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=20099344</a><p>It&#x27;s not plagiarism, but if the OP got the idea for checking for recency bias from the HN thread, they should explicitly credit that.
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olalondealmost 6 years ago
Doesn&#x27;t this analysis rest on the assumption that movies are equally good each year? Maybe I suffer from nostalgia (or survivorship bias) but I&#x27;m not sure this is a good assumption.
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iforgotmypassalmost 6 years ago
I feel like author is missing the point. Shouldn&#x27;t the recency bias show up in recent votes (while the movie is &quot;hot&quot; and trendy) vs. later votes?
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bscphilalmost 6 years ago
Incidentally, in case the creator sees this, this site is borderline unusable for me on mobile Firefox. Text gets cut off in strange places, I can&#x27;t zoom out properly to see all of the animations. &quot;Request desktop site&quot; seems to fix some things but break others - at least I can zoom all the way out but the text becomes hard to read.<p>Situation might be the same on Chrome (didn&#x27;t check), but regardless it could use some work since it&#x27;s pretty broken as is.
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djtriptychalmost 6 years ago
I was recently thinking about this as Chernobyl (which was excellent to be fair) quickly became the highest rated TV drama ever.
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ddffrealmost 6 years ago
Of course, there are plenty of examples of that. Like the assassination of the NK leader movie, which at first received 10 star rating. Now look at it.<p>Sane goes with all the new blockbuster movies, you should usually wait awhile for the real ratings to show.
dahartalmost 6 years ago
&gt; Number of Movies By Ratings<p>I’m dying to see all of these as percentages rather than absolute numbers! I was even thinking that while scrolling down through, and then there the totals are right at the bottom. @KyleOS are you up for normalizing them?
fileyfood500almost 6 years ago
I see from one of the charts that the average movie rating from 2019 is over .5 higher than the previous 5 years, in what appears to be a big jump. Is it possible that recency bias is only relevant on a shorter timescale? It looks like ratings are higher for movies that are a few months old, based on the data. I wonder if this is generally true, or if early 2019 happens to have higher rated movies.
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in3dalmost 6 years ago
I wonder if recording ratings now and then every month or so would show a decline in ratings. IMDb must know already.
ravenstinealmost 6 years ago
Great job! I&#x27;d love to see a similar analysis for Rotten Tomatoes since there&#x27;s separate metrics for critics and audience, and I find RT ratings to be more extreme than IMDb. I&#x27;m often surprised to see how many bad movies get a rating of ~6 on IMDb.
IAmEveryonealmost 6 years ago
Series tend to be rated higher than movies, probably because people that don&#x27;t enjoy them stop watching and rating after one or a few episodes.<p>That effect may well be spilling over into movies, considering far more movies are now sequels.
ajhurlimanalmost 6 years ago
An alternative way of reading the same data: &quot;Analysis of whether movies are getting better over time&quot;
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z3t4almost 6 years ago
What I find most amusing is ratings (and also awards&#x2F;nominations) before a movie has been released.
mynewstartupalmost 6 years ago
In terms of shows, Sopranos has long been dethroned, possibly due to this effect. Then again, production values will only get better over time, so maybe the latest shows are of the best quality overall.<p>Best line:<p>Fucking Queeahs! (Paulie throws chair at his murder victim spirits)