This post was inspired by the comments on my post about the passing of Walter Cronkite.
After seeing the decline in the audiences of the broadcast network evening news shows in the attached chart, people had lots of theories.
Was it the retirement of the "old guard" anchors (Cronkite, Huntly/Brinkley, etc.)? Corporatization of the news? Entertainment focus? Cost cutting? Political bias?
I think all those things may have been small factors, but I think the audience share shift from broadcast networks to cable networks since the early 80's is the major factor.
The dark blue portion of the chart below is the broadcast network affiliate share of the prime-time audience since 1984-85. It looks enough like the broadcast evening news decline to convince me that the shift is the major cause.
For more background on the audience share chart above you can see the original post here.