[ronaldx]

I believe your observation is correct, that movies are over-rated at first, but I doubt this is wholly - nor even mainly - corruption.

People who are motivated to see a movie early are the same people who are likely to enjoy that movie. This makes it natural for movies to get rated very highly when they are first released. That's just natural.

If you forced people to photograph their ticket stub, I believe this could make the problem worse: mainly people who particularly loved the movie (or thought it was significantly worthy of comment) would be motivated enough to do that. You'll just collect the IMdB's 10s and 1s.

I know many people use the IMdB for their own record-keeping. These people would stop doing that if there was an administrative barrier that made it less convenient than a paper equivalent, e.g. writing in an address book. I strongly believe this makes their votes neutral/genuine compared to other survey methods.

[JoeAltmaier]

But some 10's and 1's are lazy indignant people. Putting an obstacle in the way of registering a rating could filter out lots of noise. Leaving people who deliberately, intentionally review movies. Those ratings would be of an entire different class.

[lyndonh]

But surely they don't use the mean to find the average score ?

Even a basic trimmed statistic would find a much more accurate average. Lazy people leaving 10s and 1s would be removed or given a lower weighting.

[Retric]

As long as it's consistent such ratings are averaged out as a 8.2 is only meaningful in comparison to other scores.