From the article:
""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.""
This type of study is extremely difficult to do because of the underlying bias and subjectivity involved with politics. I think that given the inherent difficulty, the authors did their best to minimize the subjectivity as much as possible.
I am just impressed that things fell out the way most would expect...the NY Times tipping the scales way to the Left...no surprise to Free Republic, but it does give us ammunition against the Media from a study and not just Bozell's documentation (which the Media tend to ignore or disdain).