For me, I would just use the rule of thumb. i.e. (Number of staff left / the number who joined the company) x 100. If no one left and no one joined, you have no staff turnover (good); if 2 joined and 1 left, you have 50% turnover; if 2 joined and 2 left, you have 100% turnover (no good); if 1 joined and 2 left then you are in trouble. I don't know the Hay formula. I think you can any formula that suits you most.
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