It’s amazing how often people write about ratings for CNN versus Fox News Channel and miss the most obvious analogy: The difference between AM newsradio and talkradio formats.

In radio, as in TV, ratings are a function of two things: The total number of people who tune in over a span of time, or “cume;” and the average time spent listening.

In newsradio, more people tune in overall, but they don’t listen as long as a rule of thumb. They flip over to get traffic updates or a sports score, then flip away.

In talk, if you have a host someone likes, he or she will listen for a couple of hours, or at least as long as they’re in the car. So talk stations often have higher ratings, even if their cume is lower.

Fox News has the same advantage. People — mostly in their 60s or older — turn to the channel and leave it on for hours. By contrast, people tune to CNN for key events or to check out headlines, but usually don’t hang around as long.

So when CNN talks about being “sticky,” as an exec did in David Carr’s New York Times column, what he really means in funky TV jargon is better approximating the tune-in time of Fox News. But doing that also requires shifting toward a profile that’s closer to Fox, which by its nature undermines the hard-news, breaking-news, down-the-middle niche the network seeks to cultivate.

It’s a conundrum, to be sure. But it’s no real mystery. As long as CNN chooses to be a news station as opposed to a talk station, it’s going to have a time-spent-viewing issue. The question is how the network incorporates more of the latter (i.e. talk) without completely departing from the former (news) — or pandering in a way that dumbs itself down.

I don’t have an answer (and based on recent history neither does CNN), but providing less material for “The Daily Show” to lampoon — that is, being more consistently competent in its execution, as opposed to leaping after every headline without thought or context — would be a good place to start.

But it’s pretty clear CNN won’t solve the problem until it accurately frames what the challenge is. And I have serious doubts Anthony Bourdain is the recipe for what ails it.