Since the launch of AdWords in 2000, "Google has worked with advertisers and their agencies to increase brand and product awareness -- and to drive sales -- by helping advertisers reach the right person, in the right place, at the right time, through the effective use of search advertising. The success of this tactic has generally been measured by connecting search advertising campaigns to revenue within e-commerce domain. As consumers have become accustomed to a multi-channel world, however, it has become important to look outside "e-commerce box" to measure search campaign success. The goal in doing so is to find the correlation between search advertising and overall company sales, both online and offline, as customers are present in both places.
In recent times, a growing number of our customers have asked us and their agencies how they should approach the concept of quantifying online's impact on in-store sales. We recently thought through the concept with Razorfish and came up with a joint POV," informs Google.
More Info: Razorfish POV (pdf)