As social media increasingly affects streaming numbers and memes morph into hits, it has never been easier for younger artists to turn viral fame into chart success -- a sensation that Mason Ramsey, the only preteen on the 2019 list, knows better than most.

METHODOLOGY: A committee of Billboard editors weighed a variety of factors in determining the 2019 21 Under 21 list, including but not limited to impact on consumer behavior, as measured by such metrics as album sales, track sales, streaming volume, social media impressions and radio/TV audiences reached; company growth; career trajectory; reputation among peers; and overall impact in the industry specifically during the past 12 months. Where required, record-label market share was consulted using Nielsen Music market share for album plus track-equivalent and stream-equivalent album consumption units. Unless otherwise noted, Billboard Boxscore and Nielsen Music are the sources for tour grosses and sales/streaming data, respectively.

Contributors: Tatiana Cirisano, Leila Cobo, Stephen Daw, Gab Ginsberg, Josh Glicksman, Bianca Gracie, Lyndsey Havens, Carl Lamarre, Jason Lipshutz, Chris Payne, Andrew Unterberger, Taylor Weatherby, Christine Werthman