Rent-to-play modulation

Why did Yang Yan, the prime minister of the Tang Dynasty, advocate abolishing the rent system and implementing the two-tax law instead?
Tang Empire Rent-to-play modulation Don Ting Two tax laws Yang Yan Tang Dezong
01-08
The "Rent-To-Tune" System: As a system native to the Tang Dynasty, why was it so successful in Japan?
Tang dynasty Rent mediocrity Rent-to-play modulation
01-06