查到了关于8.5%rule的条文是这么说的

Section 9661 of the American Rescue Plan (ARP) simply caps marketplace health insurance premiums (for the benchmark plan) at no more than 8.5% of household income. This applies to people with household incomes of 400% of the poverty level or higher; for people with lower incomes, the normal percentage of income that has to be paid for the benchmark premium has been reduced across the board. 

https://www.healthinsurance.org/obamacare/beware-obamacares-subsidy-cliff/