Pop music these days is a hybrid beast, and this Top 20 proves it – on two counts.

Exhibit A: take a look at those oldies rubbing shoulders with all the young dudes. If it isn't literally true that half the people on this list weren't even born when the other half were already performing, it's close enough. It's the paradox of youth culture entering its dotage, in full evidence.

And Exhibit B: the fractured sources of stardom. When the Stones were as young as Taylor Swift is now, record sales were the yardstick of fame. The internet has disrupted pop music's traditional business model. Chart success has become just one of several measures of success, and a negligible one at that.

This Billboard overview of 2015's highest-earning performers in pop music shows that touring is by far the biggest source of income – with only two exceptions.

The year's biggest star in terms of earnings is Taylor Swift. In 2014, she was only 15th on the Billboard list, with a combined income of a mere $13.6 million. Last year, she increased her income more than five-fold, to $73.5 million. More than 80% of that total came from her 1989 World Tour. The exceptional nature of Swift's victory can also be expressed in money: $23.5 million – the amount by which she outperformed One Direction, the #1 for 2014.

Another measure is the distance to the #2 for 2015, Kenny Chesney. The country singer earned a total of $39.8 million, just over half of Taylor's total revenue. His big money-spinner was the Big Revival tour, making him €38.1 million.

Despite their current combined age of 289 years, the Rolling Stones came close last year to equalling that total ($39.6 million), and that touring prowess ($37.3 million).

Like Chesney and Jagger & Co., Billy Joel earned more than 95% of his 2015 earnings from performing – in his case, no more than 29 shows. Those must have been eye-wateringly expensive tickets.

One Direction, dropped to 5th place ($24.2 million), are the first performers after Swift to earn a decent buck from their actual sales. Their music sold for $3.1 million in 2015 (digital plus physical sales), more than double the amount for the Rolling Stones. They and Swift are part of the youth brigade, the three performers in between are the old guard. That pattern will repeat throughout the list.

Take the Grateful Dead, at #6: sales and streaming revenue doesn't even add up to $1 million, while touring netted the Sixties relics a total of $22.5 million.

The much younger Luke Bryan, at #7 with $23.1 million in total revenue, earned $4 million in sales alone, while U2, at #8 with $21.8 million, barely scraped together $465,000 in worldwide sales (again, that's physical and digital) last year. Even in publishing revenue (copyright earnings and such), U2 has to bow before Bryan. Only in live performance do they beat the #6. ($20.6 million vs. $17.9 million).

Adele, at #9, is an exceptional performer. By not performing in 2015, mostly. She earned her money the old-fashioned way: by selling music ($16.3 million out of $20.5 million).

Rounding out the Top 10 are Maroon 5, who beat everyone except One Direction and Ed Sheeran when it comes to streaming. But the band's 1.3 billion streams brought in under $800,000 – proof of the common complaint that streaming pays musicians peanuts, and very few of them too.

The bottom half of the Top 20 is loaded with 6 of the list's ten 'heritage acts'. Some have more traditional fans than others: Fleetwood Mac sold three times more physical than digital music, while Madonna, the Dave Matthews Band and Elton John were among the oldies who sold more digital than physical copies.

Ed Sheeran's revenue stream is atypical, in that he earned $2.5 million of his $11.6 million total from publishing royalties. Which is what happens when you write all the songs on your hit record. Few others can say something similar – to be exact: Taylor Swift, Maroon 5 and Adele.

Visualising How the World's Top Pop Stars Make Their Money https://t.co/itiShdjkwI pic.twitter.com/scHqXuD59V #dataviz #music #money

— How Much (@howmuch_net) May 16, 2016

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Sources: Table 1