Bias on eBay

Pub date January 30, 2007


TECHSPLOITATION Complain about eBay all you like — and I’m sure you have — but the gigantic online auction site has done a few things right. The company has proven that you can create a community where strangers exchange large sums of money and most of the time nobody gets burned. It’s all because of eBay’s reputation system, the software that allows sellers and buyers to give each other feedback ratings. Nobody does business on eBay without a tail of data following behind them, packed with information about what the community thinks of their trustworthiness. Oh how I wish that people in real life had such easily accessed tails.

The cool part of having these reputation tails is that anyone can study them and look for patterns. Often, what eBay researchers find reveals more about life offline than it does about how to make the winning bid for the rare Star Trek Voyager Captain Janeway–as–evolved slug dolls.

University of Maryland researcher Chrysanthos Dellarocas recently told me how eBay reputations may be falsely inflated because people are unwilling to say mean things. He and his colleague Chuck A. Wood wrote a paper on what they call the "sound of silence" in online feedback. That silence is made by all the people who don’t add their opinions to the reputation tails. That absence of feedback, Dellarocas argues, allows certain people to garner better reputations than they should. Dellarocas says he detected a strong reporting bias in reputations on eBay and speculates that people who leave feedback are statistically more likely to be positive in their comments. Those who remain silent are likely to have squelched an urge to make a negative comment — either because they fear retribution in the form of negative scores added to their own reputation rating or because it’s simply less socially acceptable to make negative comments.

To fix this problem, Dellarocas is consulting on a start-up called TheGorb, which is all about allowing people to leave feedback anonymously. The site will let users create reputation tails for professionals such as doctors and lawyers and have the option to leave anonymous comments. Dellarocas is hoping that anonymity will solve the silence vulnerability and allow people to be more candid about the service they’ve gotten. With access to more honest reputation rankings, the people who use TheGoob have a better chance of finding a genuinely good doctor.

Meanwhile, two University of Michigan researchers, Paul Resnick and Tapan Khopkar, have just done some interesting experiments measuring the difference between the ways Indian and American citizens interact with eBay. Apparently, Indians are far less likely than people from the United States to trust sellers. The reputation ratings on eBay India reflect this. Sellers get far more negative feedback. A ranking of 93 percent positive, which would be a death knell on the US eBay, is considered a worthy score on eBay India. Khopkar also found that Indians are more willing than people from the US to buy from sellers they don’t trust. "Indians were willing to send money even if they believed there was only an 80 percent chance that they’d actually get the item they bought," Khopkar says.

In controlled experiments with recent Indian emigrants and US nationals using an eBay-like system, Resnick and Khopkar found that 74 percent of people from the US were trusting enough to buy from strangers, while only 56 percent of Indians were. Khopkar speculates that this difference could be traced to the fact that India is a much more community-oriented culture than the US. Perhaps cultural influences make Indians less likely to trust strangers online because those strangers are perceived as being outside one’s trusted community. In the US, where individualism is intensely valued, there may be more willingness to give cash to unknown people.

In light of Dellarocas’s research, however, it’s also possible to argue that Indians are just more honest than Americans in their feedback. Perhaps if people in the US didn’t silence their criticisms, eBay US would look more like eBay India. Most reputations tails on eBay US show 99 percent good feedback, which seems far too cheery to be realistic. And possibly these unrealistic reputation tails are leading to unwise levels of trust in US consumers. EBay India may be less nicey-nice, but it sounds like its consumers are more willing to give balanced feedback. Frankly, I’d rather live in a world of slightly less trust than one where critics silence themselves. *

Annalee Newitz is a surly media nerd who has never bought anything on eBay but has purchased countless books from strangers on