Earlier quoted context omitted.
50% improvement for sleeping vs not sleeping at all.
That honestly seems conservative. The times I've missed an entire night I've been essentially useless or an actual detriment.
Came into work, wrote some brand new code, and since it was basically all written on that day, and all by him, it was easy to trace back to him / that event.
The whole thing was riddled with bugs, and well below his usual quality level. Most of it got rewritten fairly quick, but yeah, if he'd taken the day off and then written it the next day, time would have been saved.
I feel like it's hard to really know when you're in that state, too. Your mind is too apt to go "I'm fine."