Team velocity is multiplicative, so 2/10 of your team is out sick, velocity...
Team velocity is multiplicative, so 2/10 of your team is out sick, velocity will go down more than 20%
Self-replies
I don't got data to check, but I suspect productivity for a given person or a given day is usually some exponential looking function, ie. a few days with incredible productivity and a long tail of days with barely measurable productivity.
So obviously, planning proceeds with an assumption of linear productivity.
And I haven't even gotten to how hard measurement is.
Zeros are bad, but non-zero productivity is going to be a fuzzy measure, maybe not even reliably ordinal (e.g. one developer did 5 MRs, one did 10 MRs, that might not mean 5<10 or that 10 = 2*5 **after converting to outcomes**)
If you think zeros are productive, I think that means you failed to identify a measure at all. I'm skeptical of the completely immeasurable, like "contributed a certain j'ne sai quoi to the team" sounds like BS and maybe is a sign of a BS job.