Is that actually bad? What happened is that we learned more about the customer's rating system. I might never have had Cuban food and love it the first time I try it on Miami but then keep eating it and it turns out the first restaurant was actually not as good as I thought, I just really like Cuban food.

This actually somewhat goes into another pet peeve of mine with rating systems. I'd like to see ratings for how much I will like it. An extreme but simple example might be that the ratings of a vegan customer of a steak house might be very relevant to other vegans but very irrelevant to non-vegans. More subtle versions are simply about shared preferences. I'd love to see ratings normalized and correlated to other users to create a personalized rating. I think Netflix used to do stuff like this back in the day and you could request your personal predicted score via API but now that's all hidden and I'm instead shown different covers off the same shows over and over

Sounds like a fun startup. Vegan restaurant rating. Could do quite a few variations of it for people who care about a specific thing.

Also, yes it matters that one in a hundred ratings leaves such a large mark on your business. I know one where they go out of their way to deliver quality. They get maybe two ratings per week. The competitor left only four fake ratings. It would take 200 weeks or 4 years to get back to 5 stars.

The normalization doesn't have to be "live". You could apply the factor at time of rating and then not change it.

Then could let everyone start with 100 one star ratings. If they rate their first thing it counts as 1/101 vote. If they start with a one star rating it will be their highest ever.

Alternatively you could apply the same rating to the customer and display it next to their user name along with their own review counter.

What also seems a great option is to simply add up all the stars :) Then the grumpy people wont have to do anything.