Microsoft Media Fastest Growing U.S. Ad Network in 2009

Microsoft Media Network was the fastest growing major ad network in the U.S. in 2009, according to data from comScore's Media Metrix panel. The measurement firm estimates the network's reach was 31 percent greater in December 2009 than it was during the same period in 2008.

Collective's network was the second fastest growing among the top 15, increasing its audience by 22 percent year-over-year for the month of December, while behavioral targeting firm Audience Science came in third, with 16 percent growth.

Based on reach alone, however, AOL Advertising remained the top network, reaching 187 million U.S. users -- or around 90 percent of the nation's total online audience. Yahoo Network followed with just under 181 million users, and Google's network reached 178 million in third position. Google's growth outpaced that of its major rivals, at 13 percent year over year. AOL and Yahoo achieved 8 and 9 percent, respectively.

It's worth noting, however, that comScore estimates the U.S. online audience itself grew by 8 percent between December 2008 and December 2009. That implies an 8 percent increase in audience reach is merely consistent with growth in overall Internet use. By that logic, networks with an 8 percent rate of growth are essentially standing still, while those achieving less than 8 percent -- such as Adconion and Traffic Marketplace -- are, in fact, losing out.

In addition, as comScore Senior Vice President Jeff Hackett points out, many networks are now focusing their efforts on improving targeting among their audiences, rather than simply increasing their volume. As a result, contracting or static audience size does not necessarily imply diminished value for advertisers, or lower CPMs for publishers.