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The phrase “trickle down housing” is an anti-YIMBY smear. It’s the logical fallacy, reasoning by analogy.

The real issue is simply N > M, where N is the number of bedrooms needed in San Francisco, and M is the number of bedrooms in existence in San Francisco. As long as N > M, then there will be winners and losers.

In most of the market, the winners are decided by price, the highest bid wins. In a small part of the market, the winners are decided by luck, 100 applicants in the lottery for every 1 affordable housing unit. Everybody else loses. The goal of YIMBY is to make everybody into winners.

It doesn’t matter whether the units are built as luxury. Run-down shacks in boring neighborhoods are going for multi-millions of dollars. There are not enough homes.

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I have a different proposal I'd like to run by you... I'm concerned about congestion on California's roads. The issue is simple: at rush hour, for many popular routes, N > M, where N is the number of cars on the road, and M is the number of cars there are space for at any given time. Let's solve this problem--build more roads!!

Oh wait: https://www.citylab.com/transportation/2015/11/californias-d...

...

In all seriousness, I am on your side--zoning laws which never change create lots of incentive problems and prevent central and desirable areas from sensibly adding density. But let's not pretend this is a simple math problem where nobody with sense can disagree--it just leads to demonizing the other side (which there is lots of here).

Among other things, it will almost surely never be the case, no matter how successful YIMBY is, that N=M in the bay area, because adding more housing will increase demand--people will stop leaving to take jobs in Denver/Seattle/Portland, more people will find it doable to move to the bay area, etc.

The big difference here is that I think a lot more people in San Francisco is a good thing, and a lot more cars on the road is a bad thing.

I never specified that N = the number of people currently living in San Francisco. The outflow of people is somewhat greater than the inflow, as children of existing residents (and often their parents, too) move out and new people move in, limited by the slow growth of homes. However, when we have so many employed homeless people in the streets, it’s pretty obvious that whatever N is, N > M. https://sf.curbed.com/2017/5/10/15612746/sf-math-teacher-hou...

If we actually built housing in accordance with demand, then the population of San Francisco would be much, much higher, but it wouldn’t be unlimited. I wish San Francisco would get over itself; not everybody wants to live here. Patrick Wolff estimated that we would need 50% more homes in the next 20 years to make housing affordable. http://www.sfexaminer.com/solve-affordability-crisis-bay-are...

There’s no way we can get 50% more homes with our current system, project by project, 500 units here, 1,000 units there. We need about 200,000 units in San Francisco alone. We can get there by eliminating the density limits. Just look at the zoning maps, how much of the city is restricted to single-family homes. With the more ambitious versions of SB 827, we could have achieved 50% more homes by converting half of the single-family homes into quad-plexes, as was traditional before zoning was invented to keep poor people out of nice neighborhoods. http://sf-planning.org/zoning-maps https://www.nytimes.com/2017/08/03/opinion/sunday/zoning-law...

Adding more housing will lower prices, and lower prices will increase quantity demanded. Yes, more people will be able to stay in and move to the area. That's the point. You've not made an argument for why additional housing would increase demand (i.e. desire to move, willingness to pay).

Road expansion boosts capacity just fine. Not as cost-effectively as public transit, but it works. What it doesn't do is fix congestion. I'd argue that there really isn't anything like congestion in the housing market. Homes are discrete; you have one or you don't. There's no such thing as "extra" people in the neighborhood shrinking all the existing homes.

Belatedly... yes, you are right, I haven't described any shift in the demand curve. But so what? I was responding to a suggestion that the reason there is a housing "issue" is that demand is relatively inelastic, and exceeds supply, which is also relatively inelastic. My point is simply that demand could actually be fairly elastic, and so we should not describe the problem in this simplified way, because if that's the case, increasing supply will not reduce price very much, and so increased housing won't solve many of the problems the YIMBY cause is hoping to address which are caused by high housing prices.

In the road analogy, congestion on roads is akin to a price--people are paying for trips with their time. I was trying to make the point that adding more roads doesn't bring down the "price" of a trip substantially, just like adding some more housing in SF may not bring down the price of housing substantially.

OP responded by noting that, in their view, having more people in SF is a good thing in and of itself. If you agree, then we have no argument (this is almost surely a result of building more housing). But if you think that adding more housing would be good because it would allow low-paid workers to live closer to where they work, or many of the other reasons advanced in this thread, my point is simply that the analysis of this policy proposal requires more nuance than the kind of N > M analysis OP was conducting.

"The real issue is simply N > M, where N is the number of bedrooms needed in San Francisco, and M is the number of bedrooms in existence in San Francisco. As long as N > M, then there will be winners and losers."

No. This is a toy economic model that doesn't account for time or land constraints.

The benefits of construction do not immediately and equally accrue to all market participants. In cities where essentially all new construction is infill (i.e. San Francisco), new units will displace older, cheaper units (not always, but it does happen). Therefore, until supply actually exceeds demand, you will have winners and losers, and you must account for the losers.

Additionally, an any realistic model of housing, you will see that new construction will continue not until housing is as affordable as existing stock, but only until it is no longer profitable to build. It is expensive to do infill development, and therefore unlikely that any builder will continue to generate supply until prices match those of older properties. It could easily take decades for new construction to lower housing prices. For example, New York, Paris and Tokyo are far more dense than San Francisco, with more liberal development rules, yet are the some of the most expensive cities in the world in which to live.

It is thin gruel to say "I'm sorry you lost your currently affordable housing, but come back in 20 years, and everything will be affordable!" But this is essentially the response you are making.

N > M. We need more homes than we have. That is not an economic model. That is a simple, relatable, metric.

That is the best property of the YIMBY movement. Whether “missing middle” small apartment buildings or “social housing” hundred-unit buildings, all of those are illegal in places where they should be legal. It can be summed up in a simple metric. We need more homes than we have.

If we need 20 years of building, then we better get started now.

>This is a toy economic model

No, it's the pigeonhole principle. There is no level of economic sophistication that can sidestep the basic problem of an insufficient number of homes in the area.

That is just ignoring even the most basic economics. The quantity isn't relevant without price. The problem here isn't economic sophistication so much as few people other than timr seems to have actually read just a normal economics textbook and understood what it actually says. That most of his comments are downvoted without relevant rebuttal just shows that.

>“The quantity isn’t relevant without price”

The price depends on the quantity. Price is not baked into the walls, but comes from market conditions. How you can deny that and then claim the high ground about understanding economics is beyond me. This is incredibly easy to check: physically identical homes go for wildly different sums in different markets.

Timr argues above that 1) construction will take time, and 2) it will only continue as long as it’s profitable. No disagreement there. We need to be planning for the long term as well as the short term, and profit margins have a long way to fall before reaching zero.

No, what he is essentially saying is that far earlier than you can produce enough housing so everyone can live in the bay area, the cost of production will be higher than what people who want to live there can afford.

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