This comeback is summed up in a word: segmentation. Before other media tuned in to the idea, radio perfected program (and listener) niches with an ever-changing list of formats like all-news, talk, hard rock, soft rock, oldies, foreign language and more.
Today's media world is changing in unpredictable ways. Radio, over its lifespan, has made adaptation its specialty. When its centennial rolls around, we're confident it will be adeptly serving its listeners and marketers in ways not yet imagined.