While many Americans believe the national press is biased toward the left, a more damning charge is now being debated: Are U.S. media outlets actually corrupt? Those who believe they are point to the cheerleading during Barack Obama’s presidential campaign and to the recent reportage on the Tea Party movement.
As you may know, the Tea Party people have been branded in some media quarters as a bunch of racist, far-right loons. TV commentators on MSNBC and CNN have actually called the Tea Party folks dirty names on the air - all in an attempt to diminish the growing influence of the movement.
But a funny thing happened on the way to the gutter. Regular Americans have apparently opted to decide for themselves about the Tea Party, and the polling is interesting.
Corrections suggests that January 2010 Econometrica article "What Drives Media Slant? Evidence from U.S. Newspapers" by Jessie Shaprio and Matt Gentzkow has a more appropriate manner of examining media bias. In order to understand its relevance, we first note that in Shapiro and Gentzkow's 2006 Journal of Political Economy paper "Media Bias and Reputation", they posit consumers who do not know the quality of a news source with certainty. Their consumers have prior beliefs about the truth, read news articles, and sometimes the truth is revealed to them at a later time (so they can update, finding that the newspaper has deceived them, or not). The article finds that newspapers will optimally slant their news to their consumer bases's biases.
Returning to the original paper Corrections referred to, the authors find that, "consumer demand responds strongly to the fit between a newspaper's slant and the ideology of potential readers, implying an economic incentive for newspapers to tailor their slant to the ideological predispositions of consumers. We document such an effect and show that variation in consumer preferences accounts for roughly one-fifth of the variation in measured slant in our sample."
Corrections suggests that the cycle O'Reilly was referring to makes quite a bit of sense, in this light. First, individuals had some signal about Barack Obama as a Presidental candidate. News sources respond to that bias (and perhaps the two feed one another, though that conjecture is by no means clearly going to happen). Individuals vote for Obama, and perhaps discover, given a relatively monotonic downward trend, that they were deceived by media slant. Corrections offers Gallup Approval Rating Polling data below (click to enlarge). They bayesian update on the slant media stations have, just as the Tea Party, borne out of individual's discovery of deception by the media, occurs.
Corrections suggests that Mr. O'Reilly's article was not necessarily off-base, but was grasping at the model suggested by Shapiro and Gentzkow without explicitly mentioning it. It is in this clarifying manner that Corrections offers a clarification.