Earlier quoted context omitted.
Just to note, you can regularly ask your employees how they feel, and with enough employees get a significant measurement. So maybe they can measure the “woolly” morale impact of this. Tools like Lattice make it easy to do a “pulse” survey for this purpose. Also the great thing about doing this twice a year is you get two experiments so you can start to be confident it’s not just “Christmas makes employees 10% happie…
That assumes that your employees: 1. Know how they feel 2. Can translate that into numbers accurately.
The way my company does this is they ask a lot of questions and then mostly look at aggregates. E.g. they might ask 6 questions about "how do you feel about the size of your workload", "do you feel you have time to do the important things in your life", "are you satisfied with the amount of vacation you take", "do you feel stressed", ... and then roll those into a single "work life balance" metric (questions and specific metric entirely made up).
And actually we outsource to a survey company that does that for us, which apart from outsourcing the non-core competency, means that there is a reasonably neutral party deciding how to aggregate things (I think, I'm not involved in the survey design).
[1] Therefore this is better than perfect?