Have you looked much into the difference in "ripple effect" between increased density, and outwards expansion? It is odd how few analysts spot that systemic "housing affordability" which was common for decades, and still exists in a few dozen US cities, was enabled by outwards expansion of sufficient freedom that developers could obtain sites at true rural prices, and compete with each other to provide value for money in the finished housing development. There was no "non value added cost" extracted by site owners. This was the enabling factor in historically normal "median multiple 3" housing markets. Furthermore, the inwards land price "ripple effect" kept the price of land disciplined right to the centre, and hence intensification did result in a low site price being divided up over whatever number of units were built, which represented an "even cheaper option" in the market.
What we see in US urban areas that allow both expansion and intensification, is a median multiple of around 3, and 70% of new home buyers option for the McMansions and 30% for the townhouses and apartments which are truly an even cheaper option. This is systemic affordability. One historical observation here: the rapid building "up" of a city like New York occurred at the same time that the urban area was sprawling rapidly in several directions, and land prices were being kept low by this. I argue that the upwards building at the centre would have been stymied otherwise, by the effects I will now describe if the sprawl had been disallowed.
When this freedom for developers is removed, by growth boundaries or proxies for them, it seems to not matter how "liberal" the planners "years of supply of land" is, site owners expect "extractive" prices for their sites, which is easily tens or hundreds of times higher than the true rural price. The "extractive" price is based on "the maximum that end consumers of housing can be gouged to pay for the minimum tolerable space and quality". Developers do indeed do the calculations, but it is the vendors of sites who reap the zero-sum gains, developers are merely in a bidding war with each other to secure supply from a de facto land oligarchy. And this applies to ALL sites inwards to the city centre. This is why there is no example to be found, of a "ripple effect" on PRICES, of housing supply by way of increased density. Developers are trapped between paying site vendors "extractive" prices, and attempting to make an honest profit on the "value added" part of the project, which is swamped and squeezed by the dead site purchase and holding costs, which make up 70, 80, 90 percent or more of the price of the finished housing. Under these conditions, the rate of attrition in developers is high, and a worsening shortage of housing accrues from cycle to cycle. This is why Britain's cities, after decades of this, with ever more upzoning every cycle, are twice the density of German cities and six time the density of US cities, and yet there is a perennial shortage of housing, and median multiples from 7 to 10 even though the median home is a fraction of the size of the US one in cities with a median multiple of 3. The price of urban land is literally 300 to 1000 times higher. Paul Cheshire is the British expert on this.
Another sad unintended consequence of upzoning, is that even though only a small proportion of properties in the zone might be redeveloped, the way site prices are worked backwards "extractively" means that every property in the zone inflates to the price that developers are paying, meaning that "house prices" are pushed upwards. Every house buyer must outbid the developers, or be forced to accept the crammed product from redevelopment, which is still never "affordable" in systemic terms (or accept more inefficient locations and/or dilapidated old properties).
Have you looked much into the difference in "ripple effect" between increased density, and outwards expansion? It is odd how few analysts spot that systemic "housing affordability" which was common for decades, and still exists in a few dozen US cities, was enabled by outwards expansion of sufficient freedom that developers could obtain sites at true rural prices, and compete with each other to provide value for money in the finished housing development. There was no "non value added cost" extracted by site owners. This was the enabling factor in historically normal "median multiple 3" housing markets. Furthermore, the inwards land price "ripple effect" kept the price of land disciplined right to the centre, and hence intensification did result in a low site price being divided up over whatever number of units were built, which represented an "even cheaper option" in the market.
What we see in US urban areas that allow both expansion and intensification, is a median multiple of around 3, and 70% of new home buyers option for the McMansions and 30% for the townhouses and apartments which are truly an even cheaper option. This is systemic affordability. One historical observation here: the rapid building "up" of a city like New York occurred at the same time that the urban area was sprawling rapidly in several directions, and land prices were being kept low by this. I argue that the upwards building at the centre would have been stymied otherwise, by the effects I will now describe if the sprawl had been disallowed.
When this freedom for developers is removed, by growth boundaries or proxies for them, it seems to not matter how "liberal" the planners "years of supply of land" is, site owners expect "extractive" prices for their sites, which is easily tens or hundreds of times higher than the true rural price. The "extractive" price is based on "the maximum that end consumers of housing can be gouged to pay for the minimum tolerable space and quality". Developers do indeed do the calculations, but it is the vendors of sites who reap the zero-sum gains, developers are merely in a bidding war with each other to secure supply from a de facto land oligarchy. And this applies to ALL sites inwards to the city centre. This is why there is no example to be found, of a "ripple effect" on PRICES, of housing supply by way of increased density. Developers are trapped between paying site vendors "extractive" prices, and attempting to make an honest profit on the "value added" part of the project, which is swamped and squeezed by the dead site purchase and holding costs, which make up 70, 80, 90 percent or more of the price of the finished housing. Under these conditions, the rate of attrition in developers is high, and a worsening shortage of housing accrues from cycle to cycle. This is why Britain's cities, after decades of this, with ever more upzoning every cycle, are twice the density of German cities and six time the density of US cities, and yet there is a perennial shortage of housing, and median multiples from 7 to 10 even though the median home is a fraction of the size of the US one in cities with a median multiple of 3. The price of urban land is literally 300 to 1000 times higher. Paul Cheshire is the British expert on this.
Another sad unintended consequence of upzoning, is that even though only a small proportion of properties in the zone might be redeveloped, the way site prices are worked backwards "extractively" means that every property in the zone inflates to the price that developers are paying, meaning that "house prices" are pushed upwards. Every house buyer must outbid the developers, or be forced to accept the crammed product from redevelopment, which is still never "affordable" in systemic terms (or accept more inefficient locations and/or dilapidated old properties).