One useful contribution that Entman makes is distinguishing between three types of media bias:
- Distortion bias: News that distorts or falsifies reality
- Content bias: News that favours one side
- Decision-making bias: News twisted to serve the motivations of impartial journalists
He offers the following equation:
NS = the slant of a news item
F = the perceived facts
SWH = the skill of White House news managers
SO = the skill of opposition news managers
BE = decision biases arising from evaluation of the political game
BM = decision biases arising from market competition
BI = decision biases arising from personal ideology
E = event context and other sources of variation
This equation demonstrates the complex interaction of decision biases with other factors such as the skill of a political administration's news managers.
Entman also suggests applying the Hirschman-Herfindahl index (HHI) used in economics to media slant. The HHI represents the relative power of a firm with the square of its market share percentage. Thus if one firm holds a monopoly over the market, its HHI score is 10,000 (100 x 100), but if the power is divided up among a huge number of equal competitors, their individual scores near 0. Through content analysis, something like the HHI could be applied to the media to determine aggregate slant.