"Since radio’s inception, the industry has been threatened by a number of competing technologies including: the 8-track tape, cassette recorder, digital audio devices and perhaps most prominently, television.  The advent of broadcast television in middle class America resulted in the only period of revenue loss for terrestrial radio from 1951 to 1955 (Bachman, 2005). Radio responded to television with new music driven programming models.  Later, technological advancements led to FM radio, which caused internal disruption of the industry, but inevitably resulted in the AM dial embracing talk radio, today’s most popular radio format. 

in Consumer Adoption of New Radio Distribution Systems, pág. 9