Is Everybody Listening? (1947)

This is quite an interesting documentary looking at how C.E. Hooper - quite possibly the first ratings company - uses cold-calling techniques to assemble data from American audiences to help inform sponsors and producers about radio listening habits in the United States. From Jack Benny's "Benny" show listened to by 20 million Americans each week to Walter Winchell. News, sport and comedy - "I don't hold with furniture that talks"! 400 independent stations and over 1000 syndicates take this medium to over 82% of households according to the stats! It's rather basically constructed, made largely from stock footage of the celebrities, but the narrative is really quite informative and as a bit of broadcasting nostalgia, is actually well worth a watch for a few minutes.