It would be terribly interesting to analyze the metrics that do exist to understand how the scale of each artist’s fame compares in the context of their era. Does the ultra-globalized landscape of 2015 mean Taylor is more popular now than The Beatles were in 1964, or did their fame touch just as many fans, without the help of memes and digital distribution?
One interesting metric to compare would be mean annual profitability of individual artists (or bands), adjusted for inflation, during their five peak years. Limiting the measure to the peak of their careers should filter out most indirect profit such as revenue from rights to other artists’ work, though including this income would also be interesting. Including many artists in this study, and removing outliers, would give insight into how the passage of time has affected profitability. Alternatively, focusing solely on outliers (like those mentioned in the original article), would also yield interesting insights.
As I type this, I am quite convinced research of this type already exists. I would love to see it.