I have been interviewing candidates regularly for over a decade. What the candidate says on his resume and the actual level of his skill is not at all correlate

I have been interviewing candidates regularly for over a decade. What the candidate says on his resume and the actual level of his skill is not at all correlated. I have met many very good candidates that were obsessively worrying about gaps in their knowledge. At the same time poor candidates seem to be very confident thinking they are master developers but can't solve simplest task on a whiteboard.