You can read the original article below – but we have an update on it.

Google has announced it will be abandoning the current “Bayesian average” for companies with less than 20 reviews and is moving to a standard method of calculating the review average for businesses to reduce confusion.  This has already begun and is being tested in most areas of the United States and Canada. We don’t know how long the roll-out will take at this time.

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A question that seems to pop up periodically is the question, “Why is my Google Review Average wrong?” or “Why do I have 4.8 or 4.9 stars when I have only 5-star reviews?” Well the answer is in how it’s calculated.  It’s not actually an average in the traditional sense.


Google is using what is called a Bayesian Average which is basically an extrapolation using other data not visible to come up with a more realistic picture of the data. This is usually used in mathematics for studying populations.

“A Bayesian average is a method of estimating the mean of a population consistent with Bayesian interpretation, where instead of estimating the mean strictly from any or all available data set, other existing information related to that data set may also be incorporated into the calculation in order to minimize the impact of large deviations, or to assert a default value when the data set is small.” (source: Wikipedia)

Google’s own Help Page Has the following:

Score calculation

We calculate an overall rating based on user ratings and a variety of other signals to ensure that the overall score best reflects the quality of the establishment.

In other words, when you have a small sample of reviews, Google is using its large dataset of review stars to model and estimate what your average would be IF you had more reviews. This can pose several issues:

  1. Business Owners are not aware of this issue and see it as Google making a mistake.
  2. Customers have been known to accuse businesses of having “hidden” negative reviews that they believe Google is taking into account, though this is not the case.
  3. It’s not clearly stated anywhere on the review pages that they are using external data to extrapolate a review.
  4. Even though it probably works most of the time, it is not a valid picture of the reality.

Google is making an assumption that most businesses of this type, if there was a larger pool of reviews, would have a rating of 4.8 stars based on their massive pool of other businesses with reviews.



What Does This Mean To Me?

Armed with your new found knowledge about averages that extrapolate review averages based on mathematical assumptions made on external data to your own… you can do what any business owner would do.  Try to fix it. 

The only way to fix the issue is to get more reviews. There are no exact numbers from Google about when they will stop using this method to average reviews, but the general consensus online is roughly 20-30 reviews.

Whatever that number is, you need more.  And you need more positive ones!

Having a large number of REAL positive reviews from actual customers will not only save you from the assumptions made in the mathematics, but it will help solidify your ranking on Map searches and protect your overall ranking against negative reviews.

Look here for our most-read article on reviews, removing negative and fake reviews and getting more positive reviews.