IMDb's weighted average

Have you ever noticed IMDb's ratings are not the real arithmetic average of all votes? They use a so called weighted average, meaning that some user votes have more weight than others. I don't know how exactly it works, as it's a secret formula, see their explanation below. However, there are some movies and TV shows where the "weights" change the official ratings a lot.
For instance,

www.imdb.com/title/tt1582461/ratings?ref_=tt_ov_rt
Arithmetic mean = 6.1.
weighted average vote of 4.8 / 10


www.imdb.com/help/show_leaf?ratingsexplanation

IMDb publishes weighted vote averages rather than raw data averages. Various filters are applied to the raw data in order to eliminate and reduce attempts at 'vote stuffing' by individuals more interested in changing the current rating of a movie than giving their true opinion of it.

The exact methods we use will not be disclosed. This should ensure that the policy remains effective. The result is a more accurate vote average.

Seems like a reasonable approach to me. At least in theory.

Though it still doesn't offset the way that comic book films generally receive astronomical ratings inside the first couple weeks of their release dates because of all the fan-boys going gaga over it. After a month or two Marvel ratings will generally drop down to a more reasonable and appropriate level... usually.

Yeah, I knew about this system. I think it's fair enough to give more weight to a user who has been around for many years compared to someone else who just logged in to just mess up the ratings.

Of course, the system is not perfect either (see Xanadon't comment)

@Johan: Fact is, we don't know how IMDb's secret recipe actually works. We don't know if it favors users who have been around longer, or what else.

@Xanadon't: Yes, comic art fans can affect superhero flicks' ratings in the short term, but like you say ratings will generally drop down to a more reasonable and appropriate level in the long run. If you compare Arithmetic mean and IMDb's Weighted average for Marvel Comics top-grossing blockbusters, there are usually just slight differences, like -0.2/-0.3.