The most obvious piece of empirical evidence is the reason Fox News stands out like a bar of soap in a coal scuttle. If Fox News is an exception, what is the rule?

Other obvious signs are the way certain stories are covered, or not covered. Some recent examples off the top of my head:

- Doubts about Kerry's service record vs. doubts about Bush's
- David Kay's statements supporting WMD danger in Iraq vs. his statements supporting no WMD danger in Iraq
- Good news from Iraq vs. bad news from Iraq
- Mistreatment of Iraqis by Iraq's former regime vs. mistreatment of Iraqis by Americans
- Coverage of pro-Bush books vs. coverage of anti-Bush books

I'm sure others can think of a few.

Actual surveys show that less than 10 percent of media workers identify themselves as conservative.

A hypothetical question: If the New York Times was actually being paid by the Iraqi insurgency, can you think of one major story on Iraq that would have been different?