Gentzkow and Shapiro then asked what other factors help explain a newspaper’s slant. They found that the most important variable is the political orientation of people living within the paper’s market. For example, the higher the vote share received by Bush in 2004 in the newspaper’s market (horizontal axis below), the higher the Gentzkow-Shapiro measure of conservative slant (vertical axis).

On the other hand, the politics of the paper’s owner seem to matter much less. For example, once one controls for geographic factors, there is no statistically significant correlation between the newspaper’s own slant (horizontal axis below) and average slant of papers in other communities owned by the same owner (vertical axis).