I have to wonder to what extent that's actually true. To begin with, if you have a single family home in an area with high demand, upzoning could make someone willing to pay you even more than the house is currently worth because they could still turn a profit when turning it into ten or twenty times as much housing on the same lot. In other words, the value of the house may go down but the value of the land goes up when you can build more housing on it.
On top of that, higher housing prices don't necessarily equate to a better life or even more money. If your house is worth more but you still need a place to live then you can't sell it, unless you are planning to sell it soon in which case upzoning gets you more money because developers start bidding on your house before the new housing the upzoning allows to be built is on the market yet.
If not, it's not just your house that costs more. The other ones do too, which increases cost of living. Local shops have to pay higher rents and pass on that cost to you, or can't find local workers because young people can't afford local rent, so they have to close down. Then you get higher local unemployment and more crime and homelessness. You might even lose your own job because your employer moved out. What do you think drives offshoring? High domestic costs.
And if people are only thinking about the first order effect then they might imagine downzoning is to their advantage when it isn't. Which makes them support it but only until someone shows them the math.
Remember, the world passed "peak baby" back in 2013. Population is leveling off in the developed world.
With better planning the same capacity could have been added but with way better quality of life.
I case of housing, in the US, we’re as far from free market as possible. So making assumptions about what will happen if we build more based on a naive supply and demand model isn’t going to work.
A paradigm shift is to think in terms of power distribution and policy incentives. Why would a homeowner support zoning reforms? Even if they become a minority, will they be able to get the others to not vote or vote against their own interests?
The system caps its own growth.
I mean thats not true, as you well know. London put a massive belt around it to stop it from growing, which means its artificially dense. Its population density is 4/5x of amsterdam.
The US has a predilection for urban sprawl, but elsewhere thats not the case so much in Europe because land is expensive.
And it turns out happiness makes you indifferent toward the future and the people who have to live in it.