[BrenBarn]

I think another reason people think this is that people often do not notice there is a problem until rents have risen enough that they're noticeable less affordable. And when that happens, a small reduction due to supply increase is not really enough. It's not enough for rents to "go down", they actually need to become affordable.

In places where a third of renters are spending half their income on rent (as some stats have shown for CA), it is implausible to believe that nibbling around the edges of the problem is going to result in enough of a reduction to make a difference. I haven't seen any estimates of how many market-rate units would need to be built to, say, reduce the number of rent-burdened households to 10% or 5%, but presumably it would need to be in the millions. I haven't seen any studies of supply/price issues that contemplate anything like that scale.

Just as important, such studies generally ignore the issue of inequality. It doesn't really matter what rents are; if there is someone who can afford to own multiple vacation homes that sit empty most of the year, rents should be lower.