Media bias is real :: UCLA news

The Groseclose and Milyo working paper has been out for some time, so this ain't news. For the average reader this is an accessible introduction to the method and results of the study.

A few extracts:

Groseclose and Milyo based their research on a standard gauge of a lawmaker's support for liberal causes. Americans for Democratic Action (ADA) tracks the percentage of times that each lawmaker votes on the liberal side of an issue. Based on these votes, the ADA assigns a numerical score to each lawmaker, where "100" is the most liberal and "0" is the most conservative. After adjustments to compensate for disproportionate representation that the Senate gives to low‑population states and the lack of representation for the District of Columbia, the average ADA score in Congress (50.1) was assumed to represent the political position of the average U.S. voter.

Groseclose and Milyo then directed 21 research assistants — most of them college students — to scour U.S. media coverage of the past 10 years. They tallied the number of times each media outlet referred to think tanks and policy groups, such as the left-leaning NAACP or the right-leaning Heritage Foundation.

Next, they did the same exercise with speeches of U.S. lawmakers. If a media outlet displayed a citation pattern similar to that of a lawmaker, then Groseclose and Milyo's method assigned both a similar ADA score.
. . .
Of the 20 major media outlets studied, 18 scored left of center, with CBS' "Evening News," The New York Times and the Los Angeles Times ranking second, third and fourth most liberal behind the news pages of The Wall Street Journal.
. . .
"If viewers spent an equal amount of time watching Fox's 'Special Report' as ABC's 'World News' and NBC's 'Nightly News,' then they would receive a nearly perfectly balanced version of the news," said Milyo, an associate professor of economics and public affairs at the University of Missouri at Columbia.

UPDATE: CBS News provides a roundup of the critism the study is taking.