Best practice to determine variable hourly rate

Summary:

Certain set of employees are on annual scale however their hourly pay rate varies between shift and non-shift. Ex: A person with $80000 annual salary, when working in shift (2920 hours) will have a pay rate of $27.39 and the same person's hourly rate when on non-shift (2080) will be $38.46

Have anyone came across such a need and have any best practice advice other than having two hourly bases with 2920 & 2080 annualization factors and switching basis when the person moves from one shift to other?

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