Media Slant

Say that you have to answer this research question “Does the market discourage biased reporting (media slant)? Or does the market encourage it? Matthew Gentzkow and Jesse Shapiro, two economists at the University of Chicago’s business school, set out to test this proposition, and The Economist reported on their research in just two pages. Gentzkow’s and Shapiro’s methodology is smart and imaginative! Here you go:

Sendhil Mullainathan and Andrei Shleifer, two Harvard economists, argued in an influential paper* that it may be naive to think that people care about accuracy alone. Mullainathan-Shleifer model suggests that competition is far from driving biased reporting out of the market.

That is why Gentzkow and Shapiro** tested whether newspapers cater to the biases of different segments of the reading public.

1) They measure the political slant of American news coverage.

The researchers ran computer programs that analysed debates in Congress and identified phrases that were disproportionately used by Republicans or Democrats. Having identified partisan phrases, the academics then analysed the news coverage of more than 400 American newspapers to see how often they cropped up in reporting. This gave them a precise measure of “slant”.

2) They assessed the political beliefs of different newspapers’ readerships.

They did so using data on the share of votes in each newspaper’s market that went to President Bush in the 2004 presidential elections, and information on how likely people in different parts of that market were to contribute to entities allied to either Democrats or Republicans.

Conclusion: The market encourages newspapers to cater to the biases of different segments of the reading public. They found that more “Republican” newspapers had relatively higher circulations in more “Republican” zip codes. They also calculate to what degree of slant would be most profitable for each newspaper in their sample to adopt, given the political make-up of the market it covered.

* “The Market for News”, American Economic Review (September 2005).
** “What Drives Media Slant? Evidence from U.S. Daily Newspapers” (May 2007) http://faculty.chicagogsb.edu/matthew.gentzkow/biasmeas081507.pdf

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