I rediscovered the maps and work of Alasdair Rae this morning. (He has appeared on this blog before in posts like this one here.) Alasdair works in the Department of Urban Studies and Planning at the University of Sheffield and is author of the blog, Stats, Maps n Pix. Recently, he's been publishing maps showing population densities around the world. He also gets into the details of how they're made. They are pretty cool to see.

Here are the Great Lakes.

And here is Brazil, as well as a map of the world (without any land shown). Canada and the United States barely register on this second one.

Urban environments can be dense in many different ways. This is a topic that we have discussed on several occasions here on the blog. But this working paper by Solly Angel, Patrick Lamson-Hall, and Zeltia Gonzales Blanco -- called The Anatomy of Density -- is a more scientific way of looking at it. They have come up with six measurable factors that, when combined, define urban density.

What this means is that cities achieve urban density through different kinds of built form. Hong Kong, for example, gets its density from height, even though only about 4% of its land area is occupied by residential buildings. Dhaka, on the other hand, does it through low building heights and high residential coverage. Homes occupy about 20% of the city's area. Another dimension is crowding.

But here's something that may surprise you. Most cities are actually becoming less densely populated. And, despite our best efforts to encourage more sustainable forms of development, sprawl has continued to outpace densification in the vast majority of the urban agglomerations that were studied as part of this working paper. The wealthier we become, the more space we want to consume.

Here's a graph from The Economist that speaks to this trend:

To download a copy of the working paper, click here.

Image: The Economist

There is something happening in many North American cities right now. We are starting to question the supremacy of zoning for only single-family homes.

This past summer, the state of Oregon passed policy requiring cities of 25,000 people or more to allow duplexes, triplexes, and fourplexes within their single-family home neighborhoods. Minneapolis is poised to do something similar with its Minneapolis 2040 plan (though it has been contentious). And, of course, here in Toronto we recently rolled out laneway suites all across the city. Small scale multi-family dwellings are also already permissible in some areas (though few are being built).

Some are calling this a YIMBY movement. But however you want to define it, it's an acknowledgement that, if the goal is to built up instead of out, perhaps it's time we look at the parts of our cities with the lowest population densities. I would also add that following my recent post on Paris vs. Vancouver, many seemed to gravitate (in the comments) toward the Parisian model -- even if it did result in over 50,000 people per square kilometer. Density, it would appear, is okay.

While positive, it remains to be seen whether these policy changes will result in a meaningful increase in housing supply. And a lot of that will come down to the details. As I have said before on the blog, the math can be challenging on these sorts of smaller projects, which is why you have smart people proposing things like an "inverse density" rule to help encourage more smaller scale development.

But as the saying goes, sometimes you need to crawl before you can walk. And, if nothing else, there's certainly symbolic value to what seems to be taking hold across North America right now.