Oh yeah, that 20% benchmark was established by an ancient jewish rentseeker who I think can be said to be the first documented central banker. There was more than just this one tax involved, it was a whole usurious racket. The egyptians loved it of course.
Thankfully by chance right during this period there was a massive eruption in the islands across the Agean that rained hell down on the Egyptians, killing massive numbers of them and their garbage grain crops. But of course the fallout from it was documented as being an Act of God against precisely this human traficking business.
Also note, that part of what made it so bad was the consequences of this system leading to famine and glut as the royalty of course mismanaged things telling the people what to do.
I forget the details exactly, there was a good article about it on https://mises.org Joseph, the first central banker. Or some close approximation of this.
