If worker worker A is not at risk of termination, bar any incentive program rewarding excess production, worker B will likely produce 80 widgets in 8 hours.
Ah, but didn't you say it was impossible to measure quality of work? You could only measure the time spent in the seat, right?
Now you're saying people should be judged on their outputs. Interesting change of pace.
In reality he's unlikely to draw 2x the salary for 2x the output, though, because he's operating from a deficit of information and again, the manager/hr person's main goal isn't actually efficiency.
If they're smart, though, they'll give him a performance bonus based on productivity over a minimum marker, maybe staged as productivity goes up without a quality drop to squeeze out as much as possible. At a certain point, though, money becomes less of a driver for most people so that's not the only thing they'll do. They will also tie his performance to the team as a whole, create opportunities for building 'team unity' and maybe put together artificial competition so he actually cares about team performance. Then his colleagues will push him to perform better.
Worker A and B not being interchangeable in this context, and understanding the reason for their distinction, worker B will attain the quota they've been given within the alotted time period, up to 80 units as is their capacity.
Because most people aren’t as productive as Worker B.
Having Worker B come in late and leave early sets a bad example for all the Worker As (and breeds resentment among them). Worker B staying all day and screwing around half the time and distracting Worker A so they get 8 widgets done an hour instead of 10 is bad, too.
Give me 10 average people over 5 great ones any day. Average people can get better when they work together. Great people get bored and move on. Average people are just fine for most jobs.
And I assure you that I’m decidedly average and unspectacular in every way.