This is a feature we've been asked to add to our salary comparison tool (https://peerwyse.com). The request was to be able to create peer groups that you, as the manager, thought were appropriate peers for your report. Then you would be able to see the probability the report is in the different quintiles.

In the specific context the manager requesting this feature thought their reports were being underpaid and was looking for evidence that they could use to lobby for more.