In the 20th century, genres were pretty strict. You knew a rock song when you heard it. You knew a punk song when you heard it. You knew grunge, rap, and electronic when you heard it. But as the 2000s ...

(In 2018, the Billboard staff released a list project of its choices for the Greatest Pop Star of every year, going back to 1981 - along with a handful of sidebar columns and lists on other important ...