As a follow-up to yesterday's post about infill housing and overall urban densities, let's look at some basic math.

The City of Toronto has an estimated population of 3,025,647 (as of June 2023) and a land area of 630 square meters. That means that its average population density is about 4,803 people per km2. Obviously this number will be higher in some locations, and lower in others. But overall, this is the average.

Now let's consider how many people we could actually fit within the existing boundaries of the city (city proper not the metro area) if we were to simply match the average population densities of some other global cities around the world.

Again, what this chart is saying is that if we took the same physical area (Toronto's 630 square meters) and just increased the population density to that of, say, Paris, we would then have a total population of over 13 million people and we'd be housing an additional 10,011,573 humans on the same footprint.

I am not suggesting that this is exactly what should be done. (Though, you all know how much I love Paris.) What I'm suggesting is that calling a place "full" isn't exactly accurate. How would you even measure that? What someone is really saying is that they are content with the status quo in terms of built form and density.

Note: The above population densities were all taken from Wikipedia, except for Toronto's figures, which were taken from here.

One of the reasons I’m so fascinated by cities is that it’s becoming increasingly more important to get them right. From about 1831 to 1925, London was the largest city in the world. Its population went from somewhere around 1.5 to 2 million people to nearly 7.5 million. London surpassed Beijing as the largest city and was then surpassed by New York.

Today our largest cities are significantly bigger. Tokyo has almost 40 million people and London doesn’t even make the top 10. But there’s also a broader shift taking place. According to a new report by the United Nations, most of the world’s largest cities will be in Africa and Asia by 2030. Here’s a chart from Quartz:

And the reason for this shift is because Asia and Africa are newly urbanizing, whereas the rest of the world has already urbanized. In North America, over 80% of people already live in cities.

But even though Asia and Africa are following a trend that has already taken place in the rest of the world, it doesn’t mean we should assume we know what we’re doing. Having spent time in cities like Dhaka, I can attest to the many challenges that these mega-cities are facing and will continue to face as people flood in from the rural areas looking for economic opportunities.

So while it’s important that we talk about strategies for reviving cities like Detroit – which has a population somewhere around 700,000 - 800,000 people – we should also keep in mind that we have some significant challenges ahead of us in terms of creating a sustainable urban planning agenda for the world.