How Does Word of Mouth Drive Sales?

In Retailwire:  A favorite concept that we modeled in depth a number of times.  It also merits further direct lab and online testing. Still believe there are opportunities to understand the network interactions of WOM better.   This piece summarizes 'advanced econometric modeling'. " ... According to a study organized by the Word of Mouth Marketing Association (WOMMA), online and offline consumer conversations and recommendations account for 13 percent of consumer sales, on average, which represents $6 trillion in annual consumer spending. In higher price point categories, word of mouth's impact is almost 20 percent of sales. ... "