To be fair, you didn’t mention any “claims to the contrary”, and we’re commenting on a post about affordability.

You’re looking at only one factor: cost. Affordability is a ratio of income and cost. If you increase cost but also increase income, affordability can stay the same or even increase (as housing cost is only one component of total living costs). Glaeser provides very strong evidence that increasing density increases productivity and as a result paychecks. This comes directly from geometry: shorter distances not only save time during your day, but more importantly connect you to a greater set of services, talent, etc. to be more productive. But this doesn’t just apply to the white collar jobs, it applies across the board. You’ll find that even teachers in Manhattan make 3x the salary that they would elsewhere in the country.

My point is, if you densify across the board then you increase productivity across the board and salaries across the board. Housing prices go up, but everyone makes more.

Actually, this is fundamentally why prices are always higher in dense cities than sparse towns. Your earning power goes up dramatically with density, and people with more earning power drive up the price of homes that are in limited supply due to geography of cities (and man-made building policies).

To be sure, where we set the bounds of analysis, as your response reveals, greatly influences results. My point, though, was to talk about whether density drives up housing costs. I understand marginal analysis well enough, certainly well enough to appreciate that the neo-classical/Keynesian theoretical asumptions and perspectives , which have gained popularity in our development discussions, are fraught with application problems–sometimes to the point of insidious results, such as most of our ecological problems.

What if ALL housing became more dense, thus more effecient, more effective, more desirable, and more expensive? What if everyone moved into dense communities and was willing to spend a larger portion of their income on housing? Could we then say that density puts upward pressure on prices? Or, do we just say that density wasn’t the causal factor, the causal factor was desirability or efficiency, which the density caused, because it’s possible to create density without these results? Since I expect the latter a popular answer, I ask, so what? How does limiting analysis like that help us understand likely, actual outcomes, as opposed to these theoretical ones where people quickly move into new units in response to incrimental price changes and do all kind of other things to satisfy the assumptions of marginal theory?

btw – any time there’s a factor moving price, demand, or supply, the system effects are not going to mitigate that effect to zero. If it did, the system would die, and things would settle to stasis. It’s precisely the inefficiencies and the fabric of system delays that give live.

Every new unit built in Seattle allows one more household to afford a home here.

What might these forces be? I think that density is one–density of shops, of restaurants, of entertainment, of housing, of jobs, etc.

Density seems to operate akin to adding road capacity by fertilizing opportunities, diversity, social interconnections, and the like. Just as new road capacity still induces new demand, added residential density induces activity now makes the locale more desirable, thereby driving up rents.

As a thought experiments, build a dense neighborhood with a complex fabric of amenities and opportunities then locate it on Yesler between 23rd & MLK. I’m guessing that rents and property values would rise within and adjacent.

If, however, the point is only to say that all-things-equal more housing per acre will place downward pressure on rents, well of course. I’m not sure what the value of that line of thinking might be, as nothing happens in a vacuum, on a frictionless plane, or ceteris paribus. Such exercises are helpful in understanding parts of the system and forming a marginal analysis for a factor, but not much more. In complex systems, this seems to lead us humans toward tenuous conclusions.

These are often overlooked and ignored factors, however, every parents and family share these common issues.