Second, are papers across the nation collectively biased? Both left and right have argued that they are (in opposite directions of course). Well, it turns out that collectively they are slightly left leaning, in the sense that the US newspapers collectively have an average slant that corresponds to a 47% republican complexion whereas during the period of evaluation republican support was around 53%.

Third, is this bias politically driven, for instance by the reporters? Economists would like to explain actions in terms of utility maximization. And newspapers are for-profit businesses so their utility has a lot to do with profit which means sales. If we start with the idea that left/right readers like to read left/right papers and if the left are better educated and read more, then the slight left leaning bias could just be a rational market response by the newspapers. The authors look at the relationship between slant of papers and the political leanings of their geographical catchment area and find that there is a clear relationship. Further, they estimate that if newspapers were rationally maximizing profit within each catchment then the average political slant should turn out to be equivalent to a 46% republican complexion. And the papers are slightly to the right of this profit maximizing point.