So what?
The percentage of rent that is taxes is exactly the amount paid in taxes by the landlord. Period. It is an absolute number.
Why do they need to have an effect on rent for you to understand that you're paying them?
Bobby gave Lisa $10. Lisa then gave $3 to Uncle Sam. What percentage of Bobby's money went to Uncle Sam? 30%. It's that simple.
No I'm not. This is pretty entry level econ material. Price elasticity is very well studied and there's plenty of resources to learn more about it.
So what?
The percentage of rent that is taxes is exactly the amount paid in taxes by the landlord. Period. It is an absolute number.