Make Bone(s) Partially Inherit Rotation From Parent?

Like the subject line says. I want a bone which only inherits a proportion of its parent bone’s rotation but I can’t figure out how. The option is a checkbox for on or off, but I’m thinking there must be a way to set it to say 50% (so that if the parent rotates 30 degrees, the child rotates 15 degrees, or what have you.

Is there a way to do this?

Child of constraint with influence set to 0.5

Thanks Richard!