Google announced they are now adding product ratings, one to five stars, on their product listing ads in the Google search results.
Google said they are doing this because it provides "critical information to shoppers making purchase decisions." The ratings are compiled through multiple sources including merchants, third party aggregators, editorial sites and users.
Google said in their tests, the product ratings lead to a higher click-through-rate.
Here is a screen shot:
Product ratings are available to merchants targeting the United States who choose to share all of their product review content with Google, either directly or through an approved third party aggregator.
Forum discussion at Google+.