Via Ace of Spades:

MSNBC
28% of airtime studied was devoted to the 2012 election
10% of airtime studied was devoted to Obama
A subset of that Obama airtime was coded “citizenship and religion rumors” to include “birther” coverage, which was 92% of the Obama coverage

Birther fraction: .1 * .92 = 0.092, or 9.2%, or just shy of 10% of all available airtime devoted to Birther issues. Of all available airtime, nearly ten percent was spent on Birther stuff.
 

Fox
16% of airtime studied was devoted to 2012 election
5% of airtime studied was devoted to Obama
A subset of that Obama airtime was coded “citizenship and religion rumors” to include “birther” coverage, which was 8% of the Obama coverage

Birther fraction = .05 * .08 = .004, or 0.4%, four tenths of a percent of all airtime devoted to Birther stuff. Less than one twentieth of the airtime MSNBC spent.
 
Here’s the shocker

CNN
11% of airtime studied was devoted to 2012 election
5% of airtime studied was devoted to Obama
A subset of that Obama airtime was coded “citizenship and religion rumors” to include “birther” coverage, which was 100% of the Obama coverage.

Birther fraction: 0.05 * 1.00 = 5%. A full five percent of CNN’s airtime was spent on Birther issues.

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