PMP is irrelevant

PMP certification is irrelevant as a core project management competency or characteristic as valued by IT managers [US..] nationwide.
Deborah H. Stevenson, Jo Ann Starkweather

A very interesting study by Stevenson and Starkweather shows that PMP certification is not considered very relevant by IT managers and executives. Read more about that research by clicking here!

So the question remains:

"What problem does certification solve?"