Google is expected to unveil a tool that measures Internet use to help advertisers identify the best places to buy ads that will reach their target audiences, according to a Wall Street Journal report.

The measurement tool, which will be offered free to advertisers and their agencies, will compete with services offered by established leaders Nielsen and ComScore. While those services base their estimations on selective surveys or customer panels, the newspaper said, Google's results will be based on data collected from Web servers, providing a deeper and broader picture of Internet behavior.

By giving away the new tool, Google could attract more advertising business. The announcement follows one last week about Google Trends' new service, which lets people type in specific domains and compare basic traffic information about any .com site using nothing more than organic user searches.

Included are daily traffic numbers in users (sent from Google search), where the users are coming from, and related sites that were either searched for or visited in that same session. After news of the planned tool hit the Web on Monday, ComScore shares fell $1.69, or 6.1 percent, to $26 after-hours trading. Nielsen is a privately owned company.


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