Popular products on Amazon have significantly increased the number of reviews and raised the overall star rating since the company introduced one-tap ratings last year.

Last October, Amazon expanded product reviews by allowing shoppers to leave a star rating without a written review. Since then, the overall star rating has been based on traditional written reviews, one-tap ratings, and global reviews from Amazon’s international marketplaces.

For example, Apple AirPods currently have a 4.8 out of 5 rating based on 195,483 global ratings. Only 21,467 of those ratings are traditional reviews; the rest - nearly 90% - are the one-tap ratings. For the last four months, it has been receiving over 1,000 new ratings a day.

Apple AirPods are in the Headphones category on Amazon. The average number of reviews per product increased from over 4,000 in 2019 to nearly 25,000 in October 2020 for products in the top 100, while the average rating rose from 4.1 to 4.4 out of 5. Half of the top 100 are now products with at least 10,000 reviews, more than double the amount a year ago. Many other categories exhibit the same change.

Shoppers are more likely to leave no review and instead use the one-tap rating when they had a positive experience. That’s why Apple AirPods have 173,274 five-star ratings, of which only ten percent are traditional reviews. Compared to one-star ratings, where regular reviews represent nearly half of all ratings.

As a result, Apple AirPods had a 4.4 rating twelve months ago, but as more shoppers used the one-tap rating system, the overall rating rose to 4.8 out of 5. The higher rating likely more accurately reflects all purchasers’ experience, many of which previously didn’t bother writing a review.

But, Apple AirPods now have 2,396 one-star ratings without a written review. They are worthless for future shoppers trying to decide what are the reasons some dislike them. Those ratings are also not useful feedback to brands that previously relied on reviews to inform future product changes. Additionally, ratings are less transparent than reviews since Amazon doesn’t show who and when left it (data points some people and external tools used to check for fake reviews).

Amazon has removed the friction of writing reviews - a one-tap rating takes significantly less time. Unsurprisingly, that has resulted in popular products amassing ratings more rapidly and led to higher overall star ratings. Amazon’s own Echo Dot now has over 700,000 ratings - it only had 68,000 a year ago. Most shoppers browsing Amazon see more choices they would trust, even if many are unfamiliar with the introduction of ratings.

In many categories, the top sellers now have tens of thousands - or, sometimes, hundreds of thousands - of ratings. That means new entrants have to do more to compete against what appears universally-liked products. Also, since products now more easily gain ratings, they drown out some of the fake reviews.

Still, Amazon will always have fake reviews because of Goodhart’s law, named after British economist Charles Goodhart. The law states, “When a measure becomes a target, it ceases to be a good measure.” Reviews as a measure of product quality is the target brands optimize for, and bad actors cheat for; thus, they are not a good quality measure. “There is a general rule in social and economic life: Given any system, people will find a way to exploit it,” wrote W. Brian Arthur.

The one-tap rating system has improved the perception of reviews on Amazon - more products have more reviews and better ratings - but reviews are still an unreliable signal.