## IMDb Movie Ratings Over the Years

It’s time for a random dose of statistics courtesy of The Internet Movie Database. Let’s consider all movies that have been released theatrically over the last 60 years and see whether there is a trend in their perceived quality over time. That is, do new movies generally receive higher or lower scores on IMDb than old movies?

Before looking at the numbers though, we need some rules to clarify what types of movies we are considering:

- We only consider theatrically-released films — no straight-to-video movies or TV movies.
- Short films that were released theatrically (such as Pixar’s Presto)
*are*included. - We only consider movies that have received 1000 or more votes. This restriction is to prevent movies with only a handful of votes from skewing the results too much.
- The theatrical release date of the movie must have been at least as recent at 1950.

IMDb contains 10034 movies that satisfy the above criteria. The average score (on a scale of 1 to 10) of those movies is 6.38 and the median score is 6.6. The average score per release year is given by the following graph:

As you can see, older movies (1950 – 1975) have abnormally high scores, as do very recent movies (2000 – 2009). These differences are indeed statistically significant. For example, the p-value associated with the test that the mean score in 1950 is the same as the mean score in 1989 is less than 10^{-19}. The p-value associated with the test that the mean score in 2008 is the same as the mean score in 1989 is about 0.0021. Other nearby years give similar p-values.

So this tells us that, in general, particularly old movies receive the highest scores, followed by newly-released movies, followed by “semi-old” movies from the 1980’s and 1990’s. So why the differences? Were movies from the 1980’s really just that bad? Possibly, but the more likely explanation is that movies from the 1950’s through 1970’s have artificially higher scores because people don’t generally go back and watch the crummy movies of the last generation, so they get forgotten and do not have 1000 votes on IMDb. Will people be watching Disaster Movie in forty years? I sure hope not.

On the other hand, particularly recent movies tend to draw a fair amount of hype and fanboyism. Remember when *The Dark Knight* had a score of 9.8 and was at #1 on the IMDb top 250? Now, one year later, it has a score of 8.9 and is located at #9 on the top 250. It will likely dwindle a little further down over the coming years as well.

### The Best and Worst of Each Year

While we’re looking at ratings of movies over the years, I suppose I might as well provide a list of the best and worst movie of each year (based on the votes of IMDb users), since such a list is not available on the IMDb website itself to my knowledge. Keep in mind that, as before, only movies with 1000 or more votes are considered. Enjoy!

**Downloads:**

- IMDb rating data [.zip of an Excel spreadsheet -- 341KB]
- IMDb rating data [tab-delimited plaintext -- 0.97MB]

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