Ask HN: How does your team / company measure productivity?

There are two contexts I'd like to consider.

a) When COVID first broke out, many companies moved to remote work. If your company did this, how did you measure productivity before & after the shift to remote work?

b) A few companies have done trials of a 4-day workweek and claim that productivity increases. If your company was to do such a trial, how would you measure it?