alt Hacker NewsMost rent payers aren't concerned with the exact function that will describe the shape of the curve for decline in cost of rent.
They are mostly interested in "rent go down", or at least "rent not go up".
That said, there are people who have studied this. You don't need Newtonian level math to calculate elasticity. Hell, we can look at how rents rise in a constrained market and make a pretty good guess what would happen if supply increases.
There are dozens of papers that have these numbers when you search the academic databases for "rent elasticity"
Lots of places in the world have legally mandated percentage by which rent can increase for a unit per year. It might be 2% or 3%, but it is a fixed number that is fought over politically before being decided. That is the function that you are claiming rent payers don't care about. But they do, as evidenced by elected officials enforcing the number they think will get them the most votes.