Jill Biden, wife of Vice President Joe Biden and news anchor Ann Curry (L) sit during an airing of NBC's "Today" show during a job fair for military veterans and spouses aboard the U.S.S. Intrepid Sea, Air, and Space Museum March 28, 2012 in New York City. Television’s bare-knuckle competition to rule the morning air is nothing new. But the networks upped the ante this week -- "Today" hosted Sarah Palin. - 

Jeremy Hobson: It's been a big week for morning TV shows. NBC had Sarah Palin as a guest host, ABC brought in Katie Couric and CBS had an interview with Oprah.

Reporter Elizabeth Wynne Johnson tells us why the morning shows are so important to the networks.

Elizabeth Wynne Johnson: NBC’s “Today” show is a ratings juggernaut, averaging almost five million viewers a week. This week, they added a familiar face.

"Today" clip:  'Aw, honey – see I told you – it’s Tina Fey!’ 'Not Tina Fey. It is Sarah Palin.'

Meanwhile, over on ABC:

"Good Morning America" clip: Hi everyone. I’m Katie Couric and I’m thrilled to say ‘Good Morning America’!

These morning talk shows account for a big chunk of the networks’ ad revenue. Industry watchers estimate the "Today" show’s haul at more than 450 million, with "GMA" at some 314 million.

Analyst Brian Bueno at the research firm IBISWorld says morning shows also command a premium from advertisers.

Brian Bueno: Because they are live and people don’t skip through commercials.

The rise of social media opens up other ways to get people talking about you. Shari Anne Brill is a veteran audience analyst.

Shari Anne Brill: You want people who tweet, who are on Facebook, to have that whole social media machine going as well. 

But it always comes down to ratings. And this week ends with No. 1 “Today” and No. 2 “GMA” -- pretty much where they started. 

In Washington, I’m Elizabeth Wynne Johnson for Marketplace.