For those interested in the Research Online Purchase Offline (ROPO) effect, Paul Morris at the blog Search Muse has assembled a list of case studies, market research, and articles on the topic.
While there’s general agreement that people rely on online research to make decisions about offline purchases, ROPO statistics are notoriously often difficult to come by. Morris acknowledges that there “is no magic ROPO knowledge bullet.”
But he does link to examples of companies who have measured the ROPO effect on their customers and it’s worth the time to scan the blog post for the ones most relevant to your industry.
You’ll find plenty of ROPO resources at searchmuse.com.