Measuring the impact of positive and negative word of mouth on brand purchase probability

Using two methods, three measures, and data covering a large number of categories, we present findings on the respondent-assessed impact of positive and negative word of mouth (PWOM, NWOM) on brand purchase probability. For familiar brands, we find that: 1. The impact of PWOM is generally greater than NWOM. The pre-WOM probability of purchase tends to be below 0.5, which gives more latitude for PWOM to increase purchase probability than for NWOM to reduce it. 2. The impact of both PWOM and NWOM is strongly related to the pre-WOM probability of purchase, the strength of expression of the WOM, and whether the WOM is about the respondent's preferred brand. 3. PWOM and NWOM appear to be similar forms of advice-giving behavior, except for their opposed effects on choice. 4. Respondents resist NWOM on brands they are very likely to choose, and resist PWOM on brands they are very unlikely to choose. In the Discussion section, we show how our methods could be used to construct a word-of-mouth metric. (c) 2008 Elsevier B.V. All rights reserved.