In our effort to build an open, transparent community, we only allow live account holders to leave reviews. We have it set up this way to ensure that we've verified that the reviewer has had a genuine experience with the broker.
We use a Bayesian average in the calculation of the rating to ensure that a broker with few reviews starts off with a more balanced average rating, instead of an extremely high or low score based on only a low volume of reviews. This means that in the rating calculations, we automatically include the value of 7 reviews worth 3 stars each. As the broker collects more reviews, this becomes a smaller factor in the calculation of the overall rating.
For example, if a broker receives a single 1-star review, its rating would be 2.75 stars rather than 1-star. This also explains why a company that only has 5-star reviews can have a rating of 3.25 instead of 5.
Also, we give more weight to newer reviews, and less to older ones. The most recent review holds the most weight since newer reviews give more insight into current customer satisfaction.