The 50th U.S. edition of Now That's What I Call Music! was released today—featuring hits from Pharrell, Katy Perry, Lorde, and John Legend—and it's making lots of people feel old (and inspiring some interesting analyses).

English listeners may be unimpressed. While the series launched in the U.S. in 1998, it originated in the U.K. 15 years earlier; Now 87 was released there on April 7th. Last spring, we mapped how the franchise—and its many, many spin-offs—took over England, and then the world.