...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.

3) Less bias occurs when competition produces a healthy tension between a news organization's desire to conform to audience expectations and maintaining its reputation...

...The authors' great achievement is that they write intelligently about press bias without descending into a conversation-killing discussion of "objective" and "subjective" journalism. That said, I wish they'd tested their theory a bit more rigorously by applying it to the British press, which is both competitive and excessively partisan. Despite the existence of the trans-Atlantic-flavored Economist and Financial Times, the four leading papers on the British newsstand—the Times, the Independent, the Guardian, and the Telegraph—contradict the Gentzkow-Shapiro thesis. Over there, competition has spawned newspapers whose major occupation is to provide a daily reaffirmation of one's worldview.