From the Washington Post: The End of 'Network News' By Tom Rosenstiel, Sunday, September 12, 2004; Page B07
What difference will it make that the networks are ceding TV journalism to cable? Network news was built around the carefully written and edited story, produced by correspondents and vetted in advance to match words and pictures. On the network evening newscasts, 84 percent of the time is taken up by such packages, according to content analysis by the Project for Excellence in Journalism's annual State of the News Media study.
Cable news is a live and extemporaneous medium built around talk. Only 11 percent of the time is devoted to edited stories. Eighty percent is given over to in-studio interviews, studio banter, "anchor reads" and live reporter stand-ups, in which correspondents talk off the top of their heads or from hasty notes.
See: Note to a Journalist