Amazon calculates a product’s star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers, and factors that establish reviewer trustworthiness.
This was a wonderful pre vacation read to understand historical context. Short, easy to digest sections that I referred back to on my trip. My friends loved the extra tidbits I could sprinkle in while sightseeing.