Actually, they aren't similar at all. The Dead peaked within their first 4 years and crashed,burned and bounced back. Phish took 9 years to get to the same point with a steady decline before collapsing into itself. Once the phish numbers started to decline they never looked back and look like they will continue to decline to below 50% of what the Dead averaged in their sunseet period.

Of course, quantity does not equal quality but they have to be related somehow, no?