As a source of information, references were hand selected by the person with an interest in getting selected, they will like be prepped on what to say, they have zero investment in your company's success, etc.
10% you can get confirmation that you correctly spotted the candidate’s development areas. (Everyone has them, so it’s not a gotcha. But if you think the candidate needs to work on their architecture skills, their last boss confirms it but says they’re a great hire, then you can a good conversation later. “I’d love you to do X, how do we make you a great architect along the way?)
10% if the time you catch the candidate in a lie or find yourself asking “Is the best they could find someone to talk about their work?”
When I reference checked nannies, the last bucket grew to 50%. And I had one nanny give another as a reference.
It's amazing what you get if you just stay on the phone with the reference. People want to talk. They want to say something meaningful. Once the cliches are dispensed with they're forced to say something real and at that point you get to find out the real type of person you're looking at.
Just being able to provide multiple people with meaningful positions (former manager at your company, etc.) who are willing to advocate for you is a signal. There are ways to fake that signal of course, but it's still something of a filter.
