Internet reputation systems promise to create a global village by scaling up informal word-of-mouth reputation mechanisms for sharing and for creating trust, and so solve both the coordination and the trust problem for a variety of services which could not previously be exchanged. For sharing economy advocates, reputation is an alternative to regulation: in the recent book The Reputation Economy, law professor Lior Strahilevitz asks us to “imagine if every plumber, manufactured product, cell phone provider, home builder, professor, hair stylist, accountant, attorney, golf pro, and taxi driver were rated… In such a world, there would be diminished need for regulatory oversight and legal remedies because consumers would police misconduct themselves.”

Do internet reputation systems act as an effective signal of trustworthiness?

Figure 1 is the distribution of ratings for the Netflix Prize data set. Netflix ratings are not a reputation system in the sense used here, in that they are not testimonials about people: the data set consists of ratings of movies and TV shows by Netflix customers. There is every reason to believe that the ratings are independent and honest: the rater can offer an opinion freely, having no reason to expect expect reward or punishment for any particular rating. The rater also has an incentive to give a rating that matches their actual opinion, as it enables Netflix to recommend movies that better match their tastes. So Figure 1 can take this as a reasonable distribution of independent ratings.

Figure 1.

BlaBlaCar, a French sharing economy company that connects “drivers with people travelling the same way” throughout Europe, has over a million registered drivers, transports over half a million passengers every month, and is expanding rapidly. Also, it makes testimonial-based ratings available on its web site. Figure 2 is the distribution of a set of 190,000 ratings from the blablacar.com site.4

Figure 2.

Of 190129 distinct ratings, 2152 were one-star, there was not a single two-star rating, there was one three-star rating, five four-star ratings, and 187971 five-star ratings. A BlaBlaCar rating means something different from a Netflix movie rating.

With over 98% of ratings being five stars, the reputation system does not meaningfully discriminate among drivers or riders. A reputation system that does not discriminate fails as a reputation system: it fails to solve the problem of trust.5

Collusion and fear of retaliation are the reasons why there are essentially no reviews less than five stars for rides that take place. If you give a less-than-five star review then, unlike in the case of offline community-based testimonials, it is visible to the reviewee, who can give you a harsh review in return and so affect your chance of getting future rides. Do you want to defend your opinion that the driver was a bit close to the car in front, or that the car was a bit dirty, or do you just want to give a five-star review and make a note to yourself not to ride with them again? Collusion is the other side of the retaliation coin: I know I turned up late and was eating smelly food in your car and you didn’t like it, but so long as you give me five stars I’ll give you a good positive rating and we’re both better off. Neither of these factors need to be explicit or even to be very important to produce large effects, because it makes no difference to me how I rate you. One seemingly tiny difference between word-of-mouth and the internet rating system makes all the difference, that testimonials are visible to everyone including the reviewee instead of everyone except the reviewee.

The problem is not unique to BlaBlaCar. Reciprocity and collusion in the eBay reputation system has been studied here and the authors also provide an estimate of how many dissatisfied people are not rating their trustee:

The fact that from 742,829 eBay users… who received at least one feedback, 67% have a percentage positive of 100%, and 80.5% have a percentage positive of greater than 99%, provides suggestive support for the bias. The observation is in line with Dellarocas and Wood (2008) who examine the information hidden in the cases where feedback is not given. They estimate, under some auxiliary assumptions, that buyers are at least mildly dissatisfied in about 21% of all eBay transactions, far higher than the levels suggested by the reported feedback. They argue that many buyers do not submit feedback at all because of the potential risk of retaliation.

Finally, on Airbnb, reviewing of hosts by guests and guests by hosts also happens in public and is reciprocal. The Airbnb web site does not display individual numerical reviews, although it does display individual text reviews; instead it displays the average rating that a room has received in each of several categories (cleanliness, location, communication,…) together with an overall average, rounded off to the nearest 0.5 out of five. The web site is less easy to traverse programmatically, but out of well over a hundred offerings in New York, Sydney, Berlin and Paris I have yet to see a single one that is not rated 4.5 or 5.6

So even in the absence of explicit gaming, peer-to-peer internet reputation systems do not solve the problem of trust. The BlaBlaCar site fails the basic test of discriminating among almost any of the 190,000 drives that took place—it fails to deliver any useful information beyond giving the occasional sign that a driver or rider may not turn up.