Does the 4th estate deliver? The Political Coverage Index and its application to media capture

With the upswing of populist, right-wing, and EU-skeptical parties and politicians in Europe, as well as the success of Donald Trump in the 2016 US presidential elections, the media and its role in democracies are, once again, under scrutiny. To investigate whether the media fulfill its role as the fourth estate, i.e. providing another level of control for government, or whether there is evidence of media capture, first, we introduce the Political Coverage Index (PCI), a new measure of the relative positioning of media within the political spectrum. In contrast to existing measures of political positioning (e.g., language similarities, explicit endorsements, mentions of ideological references), we utilize the tonality of articles and newscasts on political parties and politicians. Then, we apply the PCI to 35 opinion-leading media in Germany, on the basis of more than 10 million news items on political parties and politicians between 1998 and 2012. Lastly, we use the PCI to investigate whether the media fulfil its fourth estate role. Our findings show that the media outlets in our sample report more negatively on governing parties, which we interpret as suggestive evidence that media is fulfilling its role as fourth estate in democracies.