Currently though, these product ratings are only available in the US, and will start appearing on PLAs on Google Search and Google Shopping. An announcement was made by the Product Manager of Google Shopping, Mike Capsambelis:
“We believe these ratings will help differentiate products across google.com and google.com/shopping and will help merchants drive more qualified traffic through Product Listing Ads. In initial tests, product ratings also helped increase click-through-rates of Product Listing Ads.”
If you are a merchant who would like to see their PLAs appear, they will have until October to share all of their review data with Google. But keep in mind that Google is giving everyone a grace period between now and October, which will allow ratings to appear on any PLAs where product reviews are available. Any ratings data can be shared directly or through approved third party aggregators. According to Google, product ratings on PLAs are going to become available in other markets in the coming months.