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I'm interested in finding research / studies on the correlation between organic and PPC CTR. I've heard panelists at Search Engine Strategies conferences cite research stating that simultaneously ranking organically and serving PPC ads for the same KW increases the chance of getting click-throughs (versus being in organic OR PPC space only). I think, but I'm not sure, that it might have been a comScore study but I haven't been able to find it on their site. Is anyone familiar with this study (or a similar study)? If so, please point me in the right direction and include a link, if possible. Thanks in advance for your help!

A site of mine is showing as example.com instead of www.example.com in Bing and Yahoo. I know where to set the preferred domain  to www in Google Webmaster Tools, but I can't seem to find that function in Bing Webmaster Tools. Can someone please point me in the right direction?