ComScore drops after Google unveils Web ad tool

Shares of research firm comScore Inc. fell Tuesday in a drop some analysts attributed to Google Inc.'s unveiling of a new tool meant to help advertisers determine the best Web sites on which to place ads.

ComScore shares fell $4.75, or 17.2 percent, to $22.94. Earlier in trading, the stock traded as low as $22.10.

Google made its Ad Planner tool available Tuesday. The company introduced it through its AdWords blog, saying it lets users enter their demographics and Web sites related to their target audience. Ad Planner then relays information about the sites that the company's audience may view.

"You can drill down further to get more detail like demographics and related searches for a particular site, or you can get aggregate statistics for the sites you've added to your media plan," the blog entry said.

Ad Planner is free, but it is currently available by invitation only, Google spokesman Brandon McCormick said in a phone interview.

"The goal is to help advertisers and agencies understand their audience and give them the right tools to plan effective online campaigns at scale," McCormick said.

Signal Hill Group analyst Todd Greenwald called the drop in ComScore shares overdone. He thinks Google's tool will be useful for small advertisers or businesses but says it "won't match what comScore does," saying the company has a panel of over a million users in the U.S. whose online moves it tracks.

Still, "Any time Google enters your market and starts to give away products for free it's not a good thing, at least for sentiment," he said.

A comScore spokesperson could not immediately be reached for comment.

Google's Ad Planner unveiling follows its release Friday of its free Trends for Websites tool, which lets users see how popular sites are.

Google shares rose $1.56 to $546.77.