Densely packed, walkable, and you need well over a million bucks to get into 90% of the homes in that photo. Which is why fewer people live in the area shown in that photo now than 50 years ago.
Actually that's not true, nor is block-busting going to change it.
Average family size, throughout the western world (and much of the developed world) has dropped like a stone.
That line has continued its downward trajectory since 2011.
If all other things were equal, every neighbourhood in Toronto would have seen a reduction in population of (assuming the same number of dwelling units) of about 15% over the last 50 years. But if you look at the number when most of these homes were built, the fall would be more precipitous.
That decline correlates to women having fewer children; even back in 1983 the number had declined to 1.68 children per woman, that number has since declined to 1.48. Replacement rate (the number of children per woman required to hold the population steady is 2.1)
This corresponds to 2 phenomenon, one is the advent of birth control (yay!) the other is the labour participation rate of women (also broadly a good thing, but it will affect family size).
On the latter, see the charts:
Even today we see that families with young children have the mother at home fully 20% of the time.
One other notable phenomenon is the rise of post-secondary attainment in general, but particularly for women, as this has pushed off the age of marriage and child bearing which limits the potential for larger families.
Which, by the way, I'm fine with, and I am in no way arguing against women's education or participation in the labour market; I am merely showing the clear correlation, between that and family size. PS, I think the population shrinking is a great idea, and we should do that everywhere, a world with 1/2 as many humans, over time, (naturally) would be great. It would lead to lots of affordable housing too! But I digress.
Yes, money is a barrier to entry in the housing market, but families buying cheaper homes, in cheaper places are also making fewer babies and having smaller household sizes; though, doubtless, Toronto's extreme prices may make that choice that much more difficult.
But time is as big a factor as money in family size.
Money is also a factor in terms of wages, which in entry level professions have declined markedly (adjusted for inflation) over the last few decades.
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Now, we can agree housing prices are too high relative to wages, and some combination of driving down the former and driving up the latter is desirable.
Here's your problem, so long as we keep spiking the population through different channels, we're driving up demand, which drives up price, and no developer will ever sell or rent to you for less than the market will bear.
Nor are the going to buy 1.5M homes, knock them down, build new and give you a a better price per comparable unit.
Yes, they may build more units, though not enough to keep up w/demand in the current circumstances; but even if they did, the cost of demolishing all those buildings, and reconstructing them is considerable and developers aren't doing this at-cost, they expect to make healthy profit.
You might see the average price per unit decline, but only if a 2,000ft2 home becomes a 500ft2 1 bedroom condo. How many children are we having in that home?
If you want 2 children, these days, you want each to have their own bedroom. You probably want 2 full bathrooms as well. Even if you cram that into 1,000ft2, you're looking at the same price per unit as the current house, or very close to it.
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The problem is not that we need to wipe out all SFH in favour of multi-unit living, (keep in mind I live in a rental apartment) ; that simply does nothing but further reduce family size and enrich developers.
Lets also note, those existing homes already have secondary suites in many cases and some have laneway suites as well.
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You want more affordable housing, first, stop growing demand; second, raise entry-level through median wages, by ~60% to ~ 30% respectively.
Third, stomp short-term rentals out of existence and eliminate house-flipping.
Fourth, build dedicated rent-geared to income housing for lower income families.
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You want larger family sizes, reduce the work week to 35 hours (but increase hourly earning accordingly); and mandate 4 weeks paid vacation. In combination with more affordable housing and higher entry level wages, you'll likely get your wish.