Word of mouth is more effective than traditional marketing, but difficulty proving ROI is a significant obstacle to growth.Those are two of the most significant findings to emerge from the recently released &#8220; State of Word of Mouth Marketing Survey &#8221; conducted by the Word of Mouth Marketing Association (WOMMA) and the American Marketing Association (AMA).According to the study, two thirds of marketing professionals feel that word of mouth marketing is more effective than "traditional" marketing. Reflecting this belief, 70% of marketers expect their companies will spend more money on social media in 2014, representing a bigger increase than any of 10 forms of marketing that were studied.Standing in the way of bigger investment in word of mouth and social media marketing, however, are difficulty measuring offline WOM (89%), showing return on investment (85%) and measuring online social media (79%).During the recently concluded WOMMA Summit, Brad Fay &#8211; WOMMA&#8217;s incoming Chair &#8211; announced that WOMMA is embarking on a new word of mouth measurement initiative called the Return on Word of Mouth Study to address the measurement challenge uncovered in the survey. WOMMA has retained Sequent Partners, a brand and media metrics consultancy, to oversee a market mix modeling project that will put a dollar value on consumer-to-consumer conversations about brands, both online and offline. WOMMA is in the process of recruiting brands and agencies to participate in the study.Great strides have been made in the past year or two, as modeling efforts have shown that word of mouth drives sales and also contributes significantly to marketing effectiveness, as people who are exposed to marketing often talk about it with others. This new initiative will take this learning even further and allow marketers to truly understand the value of a conversation.Ed Keller, CEO of the Keller Fay Group, has been called "one of the most recognized names in word of mouth." His new book, The Face-to-Face Book: Why Real Relationships Rule in a Digital Marketplace, was recently published by Free Press/Simon &amp; Schuster. You can follow Ed Keller on Twitter, Facebook and Google+, or contact him directly at firstname.lastname@example.org. Read all Ed&#8217;s MediaBizBloggers commentaries at WOM Matters.Check us out on Facebook at MediaBizBloggers.comFollow our Twitter updates at @MediaBizBloggerThe opinions and points of view expressed in this commentary are exclusively the views of the author and do not necessarily represent the views of MediaBizBloggers.com management or associated bloggers. MediaBizBloggers is an open thought leadership platform and readers may share their comments and opinions in response to all commentaries.