Measuring productivity like that in technology makes no sense because our work is not fungible; what and how we do it matters as much as how fast we do it. Time-based productivity measurement is for factory workers stamping out widgets. So in our revenue-based world, negative productivity makes sense.
Performance. That is what the study that found a 10x performance difference observed. There is no mention of productivity in the study. If anyone has tried to study productivity, they most certainly have not come up with a 10x moniker. It seems productivity was mentioned in this thread only because it also happens to start with the letter 'p' and someone got confused.
