Abstract: The online product review social network is a social network with product information and reviews, such as Dou- ban. com. In online product review social network, consumers can not only post product reviews, but also browse friends’ product reviews. Hence, their product purchasing decisions are under the influence of word -of- mouth ( WOM). This paper proposes two novel social influence measures, namely the frequency measure and the frequency-rating measure. Both measures include the structural characteristics of one's network. The former considers actual interaction frequency between consumers f and the latter further considers the valence of WOM. This paper employs two benchmarks from literature, namely the relationship measure and the network exposure measure. The former measures one's social influence by the number of users among his friends, and the latter refers to the proportion of users among his friends. We empirically compare the four measures. The results indicate the frequency-rating measure has the best criterion validity, which is not only in line with the relationship between the social influence and purchasing behavior as suggested by theories of the consumer behavior, but also has better statistical significance and model fit. Hence, it can be used to measure the social impact of consumers, and businesses can also use it to identify susceptible consumers. It provides a more accurate measure for verifying the effect of social influence on consumer purchase.

Key words: online product review social network , social influence , word-of-mouth , susceptible consumers , criterion validity