About that paper in Nature, “The universal decay of collective memory and attention,” which “concludes that people and things are kept alive through ‘oral communication’ from about five to 30 years,” Kevin Berger asks Cesar Hidalgo:

In your mind, what is a classic example of collective memory decay?

I thought everybody knew “Imagine” by John Lennon. I’m almost 40 and my student was probably 20. But I realized “Imagine” is not as popular in her generation as it was in mine, and it was probably less popular in my generation than in the generation before. People have a finite capacity to remember things. There’s great competition for the content out there, and the number of people who know or remember something decays over time. There’s another example, of Elvis Presley memorabilia. People had bought Elvis memorabilia for years and it was collecting huge prices. Then all of a sudden the prices started to collapse. What happened is the people who collected Elvis memorabilia started to die. Their families were stuck with all of this Elvis stuff and trying to sell it. But all of the people who were buyers were also dying.