A first set of Gentzkow’s papers studies political bias in the news media. In “What Drives Media Slant? Evidence from U.S. Daily Newspapers” (Econometrica, 2010), Gentzkow and co-author Jesse Shapiro use textual analysis of a large set of newspaper articles to classify content as more Republican or more Democrat (“media slant”). This is done using statistical analysis of phrases that differentially show up in Republican versus Democrat Senators’ speeches in the Senate. These constructed measures of media slant match well with conventional wisdom and with other, more ad-hoc and subjective newspaper political classification. Gentzkow and Shapiro then use these measures to estimate demand for newspapers, and to model the newspaper owner’s choice of media slant. They find that most of a newspaper’s media slant can be explained by the preferences of its readers rather than by the tastes of its owner. The second part of the paper tries to sort out whether the bias of individual papers is driven by “demand” – i.e. the political biases of their target audience – or “supply”, i.e. the idiosyncratic preferences of the owners. They find that it is mostly demand.
This paper is one of a few cited by the AEA in their report but well worth reading. It shines an interesting light on people who break into fits over billionaire media owners / death of public journalism etc.