Rating systems

Dan Tase
Dan Tase
May 9, 2016 · 5 min read

Before the digital era people were sharing their opinions only in face to face conversations, so in the decision making process asking friends and family was the best option. As you can imagine, it was a difficult approach, and the final decision was based on recommendations from a handful of people.

All of that changed when the internet took over. Now, besides forums and social media, companies allow users to share their experience by rating the service or sending feedback, making it easier to gather all that data in a single place.

How ratings work

Data is only useful if you put it to good use, so ratings should work like a 2 way street:

  1. Helping consumers: Ratings are making it easier to decide if a service is suitable for someone’s needs, based on feedback from the community. In other scenarios — like JUST EAT or Foursquare— it’s also helping returning customers remember how their previous experience was.
  2. Helping the business: On the other side, reviews are also helping the business by giving them a better understanding of the goods and the bads. It’s a simple way to gather feedback, and it can be used to provide better services in the future.

Rating systems

There are multiple ways ratings can be implemented, but I’m just gonna get into the most popular ones:

Binary System: One of the most popular systems is the binary one, mostly used in the form of Like/Dislike, after Facebook’s introduction in 2009. Even though this doesn’t provide a specific and accurate result, it still gives a good understanding of the agreement/disagreement with a statement.

Likert System: Another common system is the one invented by Rensis Likert, where the user is also asked to evaluate a statement based on his level of agreement/disagreement, but using a 2–10 scale instead. Most Likert items have an equal number of negative and positive positions, being symmetrical from the neutral value.

In some situations pushing the user to provide a clearer response can be done by removing the neutral value (being considered an easy option to choose when the user is unsure).


From a research done by Nielsen Norman Group, 90% of users are lurkers (read & observe, but don’t contribute), 9% of them are contributors from time to time and only 1% participate constantly, so most of the contributions on any platform are submitted by a small amount of people. Those being said, using a binary scale might result in a bigger number of ratings.

But if you take JUST EAT as an example, customers can rate on 3 different aspects: Delivery Time, Food Quality and Takeaway Service. So in 2010 when the system was designed, the team chose to provide more accurate results by using the Likert scale.

JUST EAT Ratings

Even though having to fill 3 different categories might make it harder for someone to leave a rating, it’s better on a long term basis in order to gather accurate results and manage people’s expectations.

In the decision making process users are changing their mind based on those 3 aspects so it was important to help them decide on the right restaurant.

Negativity Bias

The negativity bias is one of the things that directly affects the quality of your reviews. From the Wikipedia definition, something very positive will generally have less of an impact on a person’s behaviour and cognition than something equally emotional but negative.

Users will be more likely to leave reviews when they have a negative experience, as you can see in the example below.

PS: Mihai, if you take in consideration the 1inch crust, the overall pepperoni coverage is 60.57%.

Old reviews

Surfacing reviews is equally important in order to give the user a good understanding on the product. But when do reviews stop being relevant?

Companies are improving their service based on feedback from the community, striving to offer a better experience with every new customer. In a fast changing environment like the tech world, ratings are only relevant for a short period of time, so only surfacing those in the last 6–12 months might give customers a more accurate overview. Restaurants might improve their delivery, hotels might train their staff and taxi drivers might stop playing awful music.

There are a lot of things going on under the curtain at JUST EAT, so if you have any specific questions regarding design, the product team or the jammy environment, make sure you send me an e-mail. We’re also looking for great UX Designers in London & Bristol.

I’m Dan, Product Designer living and working in sunny London. If you enjoy what you’re reading don’t hesitate to contact me. I’m also on Twitter.

Dan Tase

Written by

Dan Tase

Design Lead at Rubber Studio. Previously at Farfetch, Just Eat, Microsoft.