Attributor, a web content monitoring and analysis platform, has crunched the numbers on Google's DoubleClick acquisition, finding that together the two companies have the lion's share of the digital marketing reach.

"The most interesting factoid is that Google has 71 percent of the long tail, and Doubleclick has nearly 50 percent of the big head," Federated Media founder John Battelle wrote on his blog.

Working with Compete, Attributor looked at ad serving data from 68 million domains. The long tail crown went to Google, which has an eight-fold advantage in terms of reach over MSN for sites that get fewer than 100,000 monthly unique visitors. By comparison, DoubleClick had a three-fold advantage over Yahoo for sites that have more than 1 million monthly unique visitors.

The data highlights Microsoft's pressing need to team up with Yahoo in its efforts to compete with Google.

Attributor's analysis can be found here.