According to the study "Impacts and ROI of Internet Local, Classifieds, and Directory Advertising" shows that online local directories can be a powerful medium to drive online and offline sales. The local space attracts highly valuable customers who are likely to convert both online and offline (though the study finds that most of the conversion occurs offline). The study offered several case studies (e.g. Verizon superpages, Cars.com, etc.) and looked at the funnel analysis for each as well as the conversion rates.

View the Powerpoint summary of the study here http://www.iab.net/resources/iab_localsearch.asp