Evaluation Manipulation

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Various studies have confirmed that evaluation systems can be of value when they are properly designed and managed (Dellarocas, 2003; Resnick et al., 2000; Pavlou & Dimoka, 2006). Sellers in online marketplaces accumulate credibility through evaluation systems and consumers put their faith in other buyers’ assessments of a seller’s credibility when making purchase decisions (Pavlou & Dimoka, 2006). Higher positive ratings increase sellers’ sales opportunities (Ba & Pavlou, 2002; Gregg & Scott, 2006). Evaluation systems can also disclose past transaction information through the evaluations of both buyers and sellers. In addition, such systems help marketplaces to automatically eliminate untrustworthy sellers by continuously accumulating rating scores. Overall, these systems enable buyers to avoid sellers who sell products of uncertain quality, thereby increasing the overall quality of sellers in online marketplaces (Akerlof, 1970). Therefore, effective evaluation systems are essential for the sustainability of online marketplaces.

2.3 Evaluation Manipulation

Because evaluation systems provide critical information for buyers’ purchase decisions, various forms of seller manipulation have emerged to encourage buyers to leave positive ratings (Huang et al., 2011; Melnik & Alm, 2002). Evaluation manipulation occurs

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when sellers attempt to influence buyer evaluation and encourage or urge buyers to write favorable comments. Although buyer evaluations are not easily manipulated, opportunistic sellers still take various manipulation schemes. Moreover, the evidence from online marketplaces suggests that evaluation manipulation continues to occur (Dini & Spagnolo, 2009).

In addition to acting as a kind of word-of-mouth testimony, online evaluations also help sellers to obtain the trust of buyers. Higher rating scores and favorable comments appeal to buyers. McDonald and Slawson (2002) point out that sellers’ evaluations are important indicators for buyers in dynamic markets, as most buyers use them to identify trustworthy sellers to reduce their transaction risk (Ba & Pavlou, 2002; Gregg & Scott, 2006). Li (2010) suggests that a seller’s credibility as indicated by an evaluation system results in more buy-it-now transactions. Sellers’ evaluations also have positive effects on the final price and the probability of a successful transaction in online auctions (Melnik & Alm, 2002; Huang et al., 2011). Evaluations also affect sellers’ net revenue (Song and Baker, 2007). On Taobao.com and many other online marketplaces, sellers’ rating scores are cumulative, with each positive rating leading to an incremental increase and each negative rating a decrease. Although neutral ratings do not increase or reduce the score, they increase

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the denominator in the fraction calculation, and thus dilute the positive ratings. Furthermore, negative evaluations always attract consumers’ attention, just as defects are easily spotted, which greatly influences buyers’ purchase intentions (Simonson, 2001). Sellers thus adopt different methods to avoid negative evaluations to maintain a good reputation.

Previous studies have found that online transaction disputes, customer complaints and manipulation behavior challenge the viability of evaluation systems (Dini & Spagnolo, 2009;

Gregg & Scott, 2008; MacInnes et al., 2005). To avoid negative evaluations, some sellers disguise themselves as buyers and leave positive comments, while others urge buyers to alter their evaluations by using intimidating language (Hu, Bose, Koh, & Liu, 2012, 2011;

Hu, Liu, & Sambamurthy, 2011). Recently, online marketplaces have begun to attract more and more manipulation behavior designed to interfere with buyer evaluations. As shown in Table 1, common evaluation manipulations include unfair ratings, identity changes, multiple accounts, feedback theft, and purchase reputations (Dini & Spagnolo, 2009). Newcomers and unscrupulous sellers frequently sell commodities at a low price as a tactic to attract buyers and accumulate positive evaluations (Dellarocas, 2003; Resnick et al., 2000).

However, some opportunistic buyers also use evaluation manipulation as a means to threaten sellers to get benefits. They may buy the cheapest thing and then intentionally leave

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a negative rating to extort money from the seller. On Taobao.com this is called “malicious poor evaluators (差評師)” (VentureData.org, 2012). “Deleting evaluators (刪評師)” also exist who use methods to help sellers to delete their negative evaluations to obtain benefits (bbs.taobao.com, 2012). In this case, the evaluator may harass buyers until they delete their negative evaluations. Unscrupulous sellers manipulate buyers not only to garner higher evaluation scores, but also to conduct fraud.

Table 1. Common forms of reputation manipulation (Dini & Spagnolo, 2009)

Form of manipulation Description

Unfair rating

A seller colludes with a group of buyers to be given ratings to gain benefits. This tactic can be used to inflate the reputation of partners or destroy competitors.

Example:

Sellers can sign up to secondary accounts or hire partners to make transactions with the primary account (competitors) then leave positive (negative) ratings to improve their reputation (destroy competitors).

Identity change

Change the identity on the online marketplace.

Example:

A seller abandons an identity with a bad reputation then creates a new

“clean” identity and continues to sell products.

Multiple accounts

Sellers use more than one account to inflate the reputation of the primary account or destroy competitors.

Example:

A seller has more than one account and uses the secondary account to purchase from the primary account and leave positive ratings to improve their reputation on the primary account. The seller can also purchase from a competitor and leave a negative rating.

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A user takes control of another user’s account to gain benefits.

Example:

A user may hack into another person’s account and leave positive feedback to inflate their own reputation.

Purchase reputation (Shill auction)

Dishonest users can sell feedback in ‘fake’ or ‘shill’ auctions by exchanging money for a positive rating by making a fake transaction.

Example:

The user sells a product named ‘feedback exchange’ or ‘new recipe gets positive feedback from all’ and then gives the buyer a positive rating.

These manipulation methods tend to involve spurious transactions that are quickly completed. A systematic form of manipulation enacted by sellers is to constantly post reminders in an attempt to influence buyer evaluation (as shown in Figure 2). These reminders include statements such as “give us full stars and you will get a discount,” “do

not leave negative or neutral evaluations without trying to resolve the problem with us,” and

“if you intend to leave a negative evaluation without contacting us first, please do not

purchase here.” The tone of the reminders ranges from prompting a positive rating to prohibiting a negative rating. Although the manipulations do not appear to be illegal, many online marketplaces restrict buyers’ comments and ratings. Therefore, this study focuses on evaluation manipulations that attempt to influence buyer evaluations by posting reminders.

This type of manipulation can be categorized as either allurement or rejection.

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Figure 2. Seller manipulation behavior on Taobao.com

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