> The case where you are able to speak to the candidate's boss because they have also left is incredibly niche.

What could be niche about this? It's the most overwhelmingly common case.

Most people change jobs every couple years and your interviewees ex-bosses are also in the industry doing the same job hopping. It is a near certainty that nearly all (if not all) their ex-bosses have moved to different companies already.

If I'm interviewing a candidate, they likely still work with their soon-to-be-former boss, who likely still works at the same company the candidate is leaving.

This is the most common case, by far.

Are you suggesting going further back, to the candidate's previous previous employer, and hoping that their direct manager from years ago is able to provide reliable and accurate testimony on the current state of the candidate ?

I said ex-boss, not current boss.

I'm surprised this is not a universal experience based on these responses. Every candidate I've interviewed has given at least one ex-boss as a reference. Every reference I've ever given has been ex-bosses.

Do you believe someone who hasn't worked with the candidate in years is a useful reference for the candidate today ?

Yes, of course. Their personality hasn't radically changed from a couple years back.

What you see in the CV is the name of the company they worked for, not the name of their direct manager.