How many online reviews are needed to optimise sales - and what's the best rating?

New research has uncovered a startling correlation between the number of online reviews a product has and its sales performance - even if some of the reviews are negative. 

The study - Assessing the Impact of Ratings and Reviews on E-commerce Performance – examined product performance on ecommerce sites, and suggests that when a product goes from having no reviews to at least one review, that product receives an average 108% traffic lift and a 65% increase in conversion rate.

The report indicates that the best-selling products in a category – those in the top 10 – each tend to have more reviews than products among the top 100 in the category as a whole, many with double or triple the number of reviews. And this is particularly marked in categories such as chocolates, skin care and baby items.

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The research, from ecommerce analytics vendor Profitero, along with dunnhumby’s BzzAgent and PowerReviews, also reveals the commercial sweet spot for both the number of reviews and the star rating – which perhaps counter-intuitively isn’t a five star review.

In terms of the number of reviews that is most beneficial, there appears to be most impact if there are between 35-50 reviews – with diminishing returns reported after 50 reviews. And brands and retailers that don’t feature ratings and reviews on their site risk losing shoppers to sites that do.  

In the absence of reviews, or enough reviews, nearly half of shoppers are reported to turn to search engines, while a quarter will go to Amazon to find reviews, and 20% will go to a competitor brand or retail site.

Elsewhere, the research into the optimal review ratings found that on Amazon UK, the top 100 best-sellers have a star rating between 4.3 and 4.7 on average.  This supports observations in the report that shoppers are more likely to purchase a product with an average star rating between 4.2 and 4.5 than one with a perfect 5-star rating. Interestingly, four out of five shoppers actively seek out negative reviews.