Increasing housing supply does not decrease home values, because high density housing benefits from network effects/economies of agglomeration. NIMBYs don't object because they think their house will be worth less, they object because they believe their quality of life will go down (based on what is important to them).
Higher density brings both good and bad:
upside: - high paying, specialized jobs - specialized, high quality services - stores open late - better dating (more fish in the sea)
downside: - more traffic - more noise - more pollution - more anonymity, crime (people in small towns leave their doors unlocked and say hi on the sidewalk)
The people who benefit most from higher density tend to be young professionals, which tend to not currently live in the neighborhood and will move in if density goes up.
> Increasing housing supply does not decrease home values
This contradicts every common theory of economics I've heard.
Well, increasing housing supply does not always decrease home value, but I also think the home value concern is a secondary distraction.
More saliently, I don't believe you're right to imply that "young professionals" only want to live in dense areas. Sometimes they have to, but that's something we can change.
Where are you thinking of when you say that young professionals move when density goes up? That does not track with my observations.
increasing supply while demand remains steady does actually lower prices.
NIMByism can be killed with a land value tax/a property tax that approximates LVT and vice versa.
It was kicked into overdrive in California thanks to prop 13 which capped property taxes.
> more traffic - more noise - more pollution
These are often true, but not inherently so. I've lived in remote rural, suburban, and dense city environments. My dense city had disadvantages, but it was quiet and had little traffic or pollution. In my experience the suburban environment is the worst for all three once you get off the residential streets, there's loud, polluting traffic (3/3).
In two of the places I lived, I couldn't keep the window open due to the constant tire noise. It wasn't an issue in the densest place I lived, which was a low-car-traffic place and pleasant to be outside in. Now, I live right next to a freight rail yard, but I don't find the train noise grating like the highway noise.