'Closing the Loop' with Online Shopping

Articles today in the WSJ and Friday in the DM News argue that the recent acquisitions of Shopzilla and Shopping.com reflect that online comparison shopping is hot and speculate about further consolidation. Empirical and anecdotal evidence suggests that while many consumers visit these sites, which are PPC lead generators for their merchants, many more use them for price research and then buy offline.

The challenge, then, for comparison shopping sites is "closing the loop" with offline buying.

U.S. consumers annually spend more than US$6 trillion in local markets. And according to the U.S. Commerce Dept.: Total e-commerce sales for 2004 were estimated at $69.2 billion, an increase of 23.5 percent (±2.1%) from 2003. Total retail sales in 2004 increased 7.8 percent (±0.3%) from 2003. E-commerce sales in 2004 accounted for 1.9 percent of total sales. E-commerce sales in 2003 accounted for 1.6 percent of total sales.

comScore ranked the various engines as follows, based on April unique monthly visitors:

• Shopping.com
• Shopzilla
• Yahoo Shopping
• NexTag
• Shop.com
• Froogle
• PriceGrabber

So how do comparison engines capture or gain credit for more of the offline buying behavior they're actually contributing to — "buy it locally" listings and pay per call perhaps?