Here is the Slate summary, which includes a link to the paper. Excerpt:
1) If a media outlet cares about its reputation for accuracy, it
will be reluctant to report anything that counters the audiences’
existing beliefs because such stories will tend to erode the company’s
standing. Newspapers and news programs have a visible incentive to
"distort information to make it conform with consumers’ prior beliefs."
2) The media can’t satisfy their audiences by merely reporting
what their audience wants to hear. If alternative sources of
information prove that a news organization has distorted the news, the
organization will suffer a loss of reputation, and hence of profit. The
authors predict more bias in stories where the outcomes aren’t realized for some time (foreign war reporting, for example) and less bias where the outcomes are immediately apparent (a weather forecast or a sports score). Indeed, almost nobody accuses the New York Times or Fox News Channel of slanting their weather reports.
Here is my earlier TCS piece on media bias.