"Bob, do you really think that losing Ron Dobson's Show (good though it might have been) could have that big of an impact on WBEN's overall numbers? After all, radio listenership in the evening hours is traditionally not that strong to begin with. Dobson must have had some really huge shares if that's the case."
He actually just needed to do as well as the rest of the station...which IIRC, he was. The syndicated stuff apparently is not. Losing a few shares at night can do two things to your overall 12+. First, it can chop a fraction of a share off the total 6 AM-midnight tally all by itself. Second, it can encourage tuneout that translates into hurting total AQH and cume because fewer radios are tuned to the station first thing in the morning, and more people have to retune their radios to come back to you. Now a majority of your morning core still will, because of WBEN's well-earned news rep. But even if only a few here and a few there don't come back in the morning, it can have a ripple effect throughout the day.
Moral of the story? Never give up on any daypart between morning and midnight where there are significant numbers of people available to you, because giving up on one daypart has a ripple effect on every other, even on the dayparts you don't change.