DEF JAM'S YOUTHQUAKE

Steve Bartels' Def Jam has no fewer than five artists in Forbes' recent 30 Under 30 list of music-biz movers and shakers.

They are, in descending order of age, singer Jeremih (29), rapper Logic (26), songwriter/artist Bibi Bourelly (22), singer/songwriter Alessia Cara (20) and hip-hop breakout Desiigner (19).

That's a pretty impressive showing for a single label, we think you'll agree. We're also duty-bound to point out that Bartels doesn't look a day over 31.