Why You Should Quit Chasing Only 5-Star Reviews

Savvy online marketers have long known about the power of the Blemish Effect, where a few poor reviews can actually increase the attractiveness of a product. A new study by Northwestern University sheds fresh light on this phenomenon and some fascinating details about the perfect average review score to secure the highest number of sales.

Five is Too Good to be True

The first big insight from the study is that perfect scores are simply too good to be true. Instead of a direct, linear correlation between scores and likelihood of purchase, the researches found that purchase intent peaks when the average star rating sits somewhere around 4.2 to 4.5 stars. When the star ratings are above this level, the purchase likelihood commonly starts to fall. Put simply, and perhaps counter-intuitively: a product with a star rating of 4.2 to 4.5 is more likely to be bought than one with a 5 star rating.

By graphing the data, we can instantly see how the likelihood to purchase dips at high review score averages for the following product categories:

Star Review Graph showing how likelihood to purchase changes with average score ratings

With a little contemplation, these findings appear entirely reasonable. Anyone who’s ever bought online will have quickly learned the merits of actively seeking out negative reviews. We also know that more than 80% of shoppers routinely do this. When there are no negative reviews to contrast against positive reviews we find it difficult to anchor our assessment and the 5-star reviews start to smell, well, a bit fishy.

The chart above also highlights the fact that shopper expectations do vary by product category, but even a relatively low involvement buying choice like lightbulbs can still be positively influenced by the presence of some lower review scores to bring down the overall average star rating.

Higher Price Means Reviews Matter More

The study also examined the role of reviews for some higher priced items including appliances and computers to try to ascertain if reviews affect buying intent differently depending on the cost of an item. Researchers found that star ratings have a stronger influence on expensive items than on low priced items within the same category. This means, entirely logically, that low priced products with low review scores are more likely to be purchased than higher priced items with low scores.

The report concludes by looking at the reasons why reviews matter, and how they can play a pivotal role in purchase decisions for unknown products or brands, items that may have a bearing on personal safety like baby food, and items that carry a high ticket price. The recommendation for marketers overseeing online sales of expensive products in high consideration categories is very clear: star rating play a hugely important role influencing buying decisions by mitigating risk and offsetting concerns about price.

In conclusion, we’ve always know that reviews are important and that having some less-than-perfect reviews is perfectly acceptable. But this new study provides additional insights into the sweet spots where average review scores lead to the highest likelihood to purchase. So, embrace those negative reviews, make sure that your higher priced items in particular have a balanced range of reviews and keep inviting more reviews so you can collect the all-important social proof we seek when buying online.