Samuel Arbesman has a fascinating post up in which he attempts to quantify the Golden Age of Television. His method was to use how long a show ran as a proxy for its quality, which seems like a decent option. By that metric, as you can see above, the period from 1950 to 1970 produced a remarkable number of long-lived shows. He also notes that there was a brief quality (or popularity) bubble in the last 1990s. That would be due to shows like the West Wing and Friends.
Completely unrelated but fascinating datapoint: 40 million American still see an episode of I Love Lucy each year. The show debuted in 1951.
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