If you can get as much shit done in 20 hours as the average employee can in 40 hours, I will assign you twice the work.

No, I won't pay you twice as much. (But as a top performer, you can expect a 5% YoY pay raise, and a 15%, instead of a 12% bonus.)

This has always been a thing that bothers me. The incentive structure is for me to be more productive than my peers rather than as productive as I can be.

LOL. Well put. This is totally the bullshit way things work in the US. You can work as hard as you can and still only make the same salary. Hell, most places I've worked have what amounts to a cost of living adjustment (the so called "performance review") of 2-5%, and, if you're lucky, a 3-5% bonus which is tied to company performance and paid annually. The inventive is always to find the smallest amount of work necessary to keep the job. That said, smart employers (like my current employer) focus on desired output. They don't care how much time it takes to get there, just so long as you do by the agreed upon date. So if you can achieve the objective that they're willing to pay you $X/year for in 20 hours a week, everybody's happy. Essentially they're paying on a freeform production basis. "We imagine that in a year you'll be able to get X done, and getting X done is with $Y to us." So far I find it immensely freeing and motivating. If I can work smarter then I can essentially work less, while still upholding my end of the bargain.

As a society we just need to stop focusing on hours and start focusing on output. But in a babysitter culture where we indoctrinate kids with the 8-hour school day and production process, this change is slow to occur. Just imagine if, in highschool, we said "here's the list of things you need to know to graduate. We provide resources on the premises--teachers, mentors, technology, books, etc--for achieving this, and it can take as long or short as you are capable and motivated. Go!" Yes, some would take forever, but I suspect many would blow through it so they could focus on doing whatever they really valued. But this will never happen because what parents really value out of highschool is the daycare aspect. While the parents are at work they can rest easy deluding themselves that their kids are 1) relatively safe, and 2) "learning" something. Safe, perhaps, but learning? Not enough, and super inefficiently. I've been in both public school and home school, and I've seen what I could do when properly incentivized. In home school I was efficiency in motion because I wanted to finish so I could go play. In public school I barely applied myself because what point was there. I'd be there for 8 hours a day, Monday through Friday, no matter what I did so...

But daycare, ahem, highschool isn't going anywhere anytime soon.

"...absolutely become more flexible ..."

There's something not quite right about this phrase.