New review article on Tim Groseclose's Left Turn

I have a new review article in Perspectives on Politics critiquing Tim Groseclose's book Left Turn that started as a blog post here way back in 2005 (gated; ungated). Here's how it begins:

In 2005, University of California-Los Angeles political scientist Tim Groseclose and University of Missouri economist Jeff Milyo published a study in the Quarterly Journal of Economics (QJE) claiming to provide quantitative evidence of what they call “strong liberal bias” in the media. Their estimates place 18 of the 20 national news outlets to the left of the centrist US voter. Not surprisingly, this claim has received a tremendous amount of media attention, particularly after Groseclose published a book based on the QJE results titled Left Turn: How Liberal Media Bias Distorts the American Mind and made appearances on “The O'Reilly Factor” and other news programs.

Few scholars of the political media would deny that media organizations tend to have different slants on the news. These differences are often significant and appear to be driven in large part by economic factors such as consumer demand and media competition. It is also true, as Groseclose and Milyo correctly note, that most journalists in the United States tend to be liberal and to vote Democratic.

However, these two facts do not necessarily imply that American media outlets have an overwhelming liberal bias. The policy preferences of reporters are only one of many possible influences on the content of the news. Numerous other competing journalistic norms and practices exist that limit the extent to which reporters' personal views influence their reporting. As a result, previous studies of partisan bias in reporting on presidential elections have generally not found consistent results. So why did Groseclose and Milyo (hereafter GM) reach such different conclusions? A closer examination of their method reveals that their estimates of media bias—and Groseclose's extensive extrapolations from those findings in Left Turn—rely on questionable assumptions about the processes generating citations of think tanks and interest groups by reporters and members of Congress, respectively.

GM's model is built on the assumption that the advocacy process in which members of Congress cite think tanks and interest groups in floor speeches somehow parallels the journalistic process by which reporters cite those groups in their reporting. This assumption is the basis for their mapping of media outlets onto a comparable ideological scale as members of Congress and the public (refer to their QJE article for technical details). If the press is unbiased, GM suggest, media outlets will cite think tanks in news reporting in a fashion that is “balanced” with respect to the scores assigned to the groups based on Congressional citations, which were measured during the 1993–2002 period. Any deviation from their definition of the political center (a composite based on a weighted average of House and Senate adjusted ADA scores) is thus framed by GM as bias.

Many objections can be raised to GM's methodology, the significant extrapolations that Groseclose makes from those findings in Left Turn, and the ungenerous tone of his responses to his critics (whom he repeatedly dismisses as “left-wing bloggers”). In this contribution, however, I will focus on GM's identifying assumption that the processes generating journalistic and Congressional citations to the think tanks and interest groups in their sample are identical. Specifically, I show how three plausible deviations from this assumption provide alternative explanations for GM's finding that the media are overwhelmingly liberal.

Read the whole thing for more.

Comments

[Matt Glassman]

Brendan:

I enjoyed the Perspectives piece. Well done.

[David in Cal]

3 comments:

1. Brendan's paper seems to discuss none of the 5 questions set out by Henry Farrell.

2. Brendan's point, that GM's research has some questionable assumptions and possible statistical flaws, would be true of pretty much every political science study that I'm familiar with. E.g., consider the studies, of which Brendan approves, showing that various economic factors determine Presidential elections. These studies draw causitive conclusions from samples that are not random and which are much, much too small to justify causitive conclusions, according to normal scientific standards.

However, I agree with Brendan that these studies are better than the usual POOMA approach. Any effort to quantify political factors will necessarily need weaker assumptions than those used in the hard sciences.

The point is, with the election models, Brendan sees the glass as half full. With GM, he sees it as half empty.

3. Brendan himself sometimes states guesses as facts in a way that he criticizes in GM. E.g., in the portion quoted above, Brendan writes, "These differences [in political slant] are often significant and appear to be driven in large part by economic factors such as consumer demand and media competition." (emphasis added)

Brendan offers no proof that these differences are driven by economic factors. IMHO these differences exist despite economic factors. The rapid success of Fox News shows that there's a big market for conservative (or less liberal) news on TV. Yet, no other cable station has tried to challenge their large marketing niche.

Here's another example of a guess atated as a fact: "As a result[of media norms], previous studies of partisan bias in reporting on presidential elections have generally not found consistent results." (emphasis added)

Are media norms really the reason why many previous studies failed to find bias? Or, is because those previous studies were done by people whose liberism blinded them to media bias? (And, would Brendan fall into this group?)