Knowledge
Aggregate rating (the star average)
The aggregate rating is the arithmetic mean of every star rating on a profile — including the ones with no words of explanation at all.
Where it comes from
On Google Maps about half of reviews are a bare star. The average therefore mixes two populations: people who wrote why they rated as they did, and people about whom nothing is known beyond the number. Scales differ between platforms — a five on Google Maps is not a ten on Booking.com.
What it means in practice
The average is good for one thing: comparing yourself against yourself on the same platform over time. It is no good at pointing to an area to fix, because a drop from 4.6 to 4.4 says neither where nor why. That is what the complaint share on a specific topic is for.