Covering breaking news -- CNN's signature -- is sure to bring in audiences when there's a big news story, but when that's not the case, the network "slumps back down to third place in the ratings," writes Alex Sherman.
CNN's rivals started with a similar strategy, but have found more success in branching out -- like MSNBC, "which now relies heavily on political analysis and personalities such as Rachel Maddow."
Dependence on breaking news can also hurt ad sales. Since they sell up to 70% of their ad inventory in advance, "the problem for cable networks is that they can’t quickly monetize surprising news events that bring in huge audiences," writes Sherman.