This is from Sherwood Schwartz' book “Inside Gilligan's Island” (don't judge):

In 1970 there was an important survey of the buying habits of TV viewers by an authoritative advertising publication. This survey revealed a tremendous difference in the buying power of urban viewers versus viewers in rural areas. Consumers in large metropolitan cities spent twice what their country cousins did, and were far more important for sponsors, and, therefore, to the networks who served them. As a result of that survey, Bob Wood, Programming Chief at C.B.S., cancelled all the rural situation comedies on his network, four of which were in the top twenty in the Nielsen ratings. The inside joke in the industry that year was that Bob Wood had “cancelled every show with a tree in it.”

I assume he's talking “Mayberry R.F.D.” and “Hee Haw,” among others. But yes, this is what helped lead to the diverse, urban, Norman Lear-style sitcom that dominated from 1971-74. Then we got our fantasy jiggle shows in the mid-70s. And by the end of the decade we'd come full circle, with “Dallas” and “The Dukes of Hazzard,” both on CBS, leading the way. And then we got Reagan.

I knew about the rural purge, just didn't know the rationale behind it.

Who knew this divide, rural/urban, country mouse/city mouse, would wind up being the great continuing battle of my American lifetime? And ongoing. Tune in next week for more exciting episodes.