We were running an operating audit of small medical offices, three to eight employees each. The hardest thing to score was how effective the practitioner was.
We pegged practitioner effectiveness to retention rates instead of reviews or conversion.
These offices rarely ask for reviews, and conversion hides it. Trust in the person actually working on you goes further than almost anything. It is very difficult to leave once you've established that trust, and it shows up as people not leaving.
Retention became the measure. It's still hard to read, because these offices are very sticky once trust is built.
Measure a relationship business by who stays, not by who says nice things.