"'The Tonight Show With Jay Leno' is once again beating rival David Letterman, whose 'Late Show' slipped back to No. 2 among yakkers in all major measurements during March.

Both shows, meanwhile, continue to erode as young viewers flee the networks for cable options like Comedy Central and Adult Swim."

There's nothing on the Big Three for youthful viewers. The average age of Letterman's viewers is 54, Nightline's 55, Leno's 56. Conan's audience wasn't much different, averaging 48 years old. Among viewers 18-34, the winner is the Adult Swim re-run of Family Guy!