We recently wrote about Clearspring, an online content sharing network, as one of the “10 D.C. Start-Ups You Need to Know About.” Clearspring’s meal ticket, the “AddThis” button that you’ve undoubtedly seen on numerous blogs and websites, has reached 1 billion global monthly users and is used by everyone from The White House to the Dalai Lama to the British Monarchy.

Publishers like ABC, AOL, Demand Media, MTV, MySpace, NBC use the AddThis button to distribute and track digital content such as links, widgets, videos, and photos to social networks, bookmarking sites, blogs, and other web services. This morning they announced a new analytics tool for their AddThis sharing platform that helps online publishers better understand their audience’s interests, so they can make better editorial decisions that drive more users and traffic to their sites. Clearspring will use their new tool to leverage the 1 billion global users and will provide publishers with an audience-based report that can be viewed within their existing analytics dashboard.

Screen shot 2010 12 20 at 11.39.02 AM Clearspring develops a new analytics tool for their AddThis sharing platform

The technology underlying their new analytics feature is the “Implicit Interest Graph,” which helps to create a digital map of the connection between people and the things they care about most. Unlike the Interest Graph created by Facebook, interests in the AddThis graph are determined by actual user behavior rather than by a user declaring interest by ‘liking’ something. Moreover, interests are displayed by levels of intensity.

“People’s interests are not binary. We do not just like or dislike something. For example, I don’t just ‘like’ movies about comic books – I love them. That difference is priceless,” says Clearspring CEO Hooman Radfar. “Using this new platform, we can understand interests more granularly. It’s like going from a black and white TV set to color.”

For more information, watch this video of today’s announcement.

Clearspring, which launched in 2006, is currently ranked #1 by comScore.