You're mixing up cause and effect. Due to NIMBYism and insufficient supply was housing able to become an "asset class" at all. Again the interest rate has been historically low in order to facilitate low rate mortgages to help people finance the increasingly costly housing market.
Of course since demand outpaced supply the added funding just caused even more inflation. (Sure, it caused some new entrants to the housing market, but since the place where people want to live is still constrained due to zoning and NIMBYism, the prices literally skyrocketed in those areas.)
No, in your own answer you pointed out the cause: "low interest rates in order to help keep housing priced up".
That is literally the cause.
NIMBYISM cannot be a 'cause' of anything - there is always more demand than supply in SF and in many places (also - people have a right to manage their own communities as they see fit.)
If a million people try move to a village, the price of the houses goes up - the cause is 'zoning'? Or is the 'cause' the the people trying to move into the village? (Propped up with huge leverage due to ever decreasing interest rates?)
The cause is that more people moved into the city than there were housing units constructed. It isn't an either-or question, it's both. San Francisco has more demand than supply precisely because an insufficient number of housing units were constructed relative to the rising population. Had the city built sufficient units to accommodate the new residents there would be no shortage of supply. Had there been no influx of residents there wouldn't be either. But we can't just outlaw people from moving into the city, so the solution is to increase the supply of housing. And NIMBYism is a big obstacle in increasing the supply of housing.
Since 1938 US government is backing housing via guaranteed mortgages. These are "money supply-side" policies that boost demand.
I'm saying that just like with healthcare and higher education, since supply is fairly limited dumping more money into those markets just raises the price.
> there is always more demand than supply in SF and in many places
That doesn't mean much. The equilibrium point is what matters. If there were more supply prices would be a lot lower. Of course desirable lots/houses/apartments will be priced higher. The problem is that house prices are going up too much, the barrier to entry (to join the community) is going up, also rents are going up (the price to stay part of the community is going up).
Plus, it's not like the demand is infinite. Let's say 10 million people want to move to SF. That's a very finite number.
And I'm not saying sure, let's build HongKong2.0.
> (also - people have a right to manage their own communities as they see fit.)
I agree with the spirit of self-determination, but alas I'm not well versed enough in the ethical problems with determining which group's interest have primacy when groups' interests overlap. After all if someone commutes every day to SF they are just as part of the community, and they might like to move closer. They want density. But this obviously quickly leads to the tragedy of the anti-commons. Everybody in that "SF community" has a vested interest in living in a nice and healthy city, but they would have to agree on how to manage housing. Usually nobody wants to voluntarily give up their advantageous spot. Nobody wants a big construction and high-rise as their neighbor. The common resource (land) gets under utilized. (NIMBYism. Plus gentrification as people who want money sell their houses to exploit this situation, which then pushes up prices of local services, which puts even more people into financial peril, who then increasingly feel that selling their property and moving is their only option.)
That sounds like a disaster or a gold-rush. What's the fair way to manage this? A quota system? First-come first-serve? The current system is rich people only.
"And I'm not saying sure, let's build HongKong2.0."
Yes you are.
If they removed controls and zoning, SF would go radically vertical, and over 30-50 years, it would be NYC/Hong Kong like.
There is no 'ethical' problem here - there is plenty of land, people can move towards Sac. and other places. Those other places could feasibly chose to build taller builddings and more density as well.
Of course since demand outpaced supply the added funding just caused even more inflation. (Sure, it caused some new entrants to the housing market, but since the place where people want to live is still constrained due to zoning and NIMBYism, the prices literally skyrocketed in those areas.)