【正文】 n is a lowimpact remendation. To assess the impact of these different kinds of remendations, we developed a way to calculate what we call wordofmouth equity. It represents the average sales impact of a brand message multiplied by the number of wordofmouth messages. By looking at the impact—as well as the volume—of these messages, this metric lets a marketer accurately test their effect on sales and market share for brands, individual campaigns, and panies as a whole. That impact—in other words, the ability of any one word ofmouth remendation or dissuasion to change behavior—reflects what is said, who says it, and where it is said. It also varies by product category. What’s said is the primary driver of wordofmouth impact. Across most product categories, we found that the content of a message must address important product or service features if it is to influence consumer decisions. In the mobilephone category, for example, design is more important than battery life. In skin care, packaging and ingredients create more powerful word of mouth than do emotional messages about how a product makes people feel. Marketers tend to build campaigns around emotional positioning, yet we found that consumers actually tend to talk—and generate buzz—about functional messages. The second critical driver is the identity of the person who sends a message: the wordof mouth receiver must trust the sender and believe that he or she really knows the product or service in question. Our research does not identify a homogenous group of consumers who are influential across categories: consumers who know cars might influence car buyers but not consumers shopping for beauty products. About 8 to 10 percent of consumers are what we call influentials , whose mon factor is trust and petence. Influentials typically generate three times more wordofmouth messages than noninfluentials do, and each message has four times more impact on a recipient’s purchasing decision. About 1 percent of these people are digital influentials—most notably, bloggers—with disproportionate power. Finally, the environment where word of mouth circulates is crucial to the power of messages. Typically, messages passed within tight, trusted works have less reach but greater impact than those circulated through dispersed munities—in part, because there’s usually a high correlation between people whose opinions we trust and the members of works we most value. That’s why oldfashioned kitchen table remendations and their online equivalents remain so important. After all, a person with 300 friends on Facebook may happily ignore the advice of 290 of them. It’s the small, closeknit work of trusted friends that has the real influence. Wordofmouth equity empowers panies by allowing them to understand word of mouth’s relative impact on brand and product performance. While marketers have always known that the impact can be significant, they may be surprised to learn just how powerful it really is. When Apple’s iPhone was launched in Germany, for example, its share of wordofmouth volume in the mobilephone category—or how many consumers were talking about it—was about 10 percent, or a third less than that of the market leader. Yet the iPhone had launched in other countries, and the buzz acpanying those messages in Germany was about five times more powerful than average. This meant the iPhone’s word of mouth equity score was 30 percent higher than that of the market leader, with three times more influentials remending the iPhone over leading handsets. As a result, sales directly attributable to the positive word of mouth surrounding the iPhone outstripped those attributable to Apple’s paid marketing 24 months of launch, the iPhone was selling almost one million units a year in Germany. The flexibility of wordofmouth equity allows us to gauge the wordofmouth impact of panies, products, and brands regardless of the category or industry. And because it measures performance rather than the sheer volume of messages, it can be used to identify what’s driving—and hurting—wordofmouth impact. Both insights are critical if marketers are to convert knowledge into power. Harnessing word of mouth The rewards of pursuing excellence in wordofmouth marketing are huge, and it can deliver a sustainable and significant petitive edge few other marketing approaches can match. Yet many marketers avoid it. Some worry that it remains immature as a marketing discipline pared with the highly sophisticated management of marketing in media such as television and newspapers. Others are concerned that they can’t draw on extensive data or e