I came across this interactive world population density map over the weekend and I immediately thought to myself, "this is going on the blog." It uses data from the Global Human Settlement Layer (GHSL) produced by the European Commission and by CIESIN (super long name) at Columbia University. And it's a fascinating way to explore how our world is urbanizing.

What you will want to do is make sure that you head over to China and check out regions like the Yangtze River Delta (shown above). If you hover over a location, it will also bring up a graph and table showing you how that place has evolved from 1975 to 2015. Note: Shanghai's peak population density in 2015 was 104,400 people per square kilometer!

According to this recent report by Smart Growth America, which looked at "walkable urbanism" in the largest 35 metro areas in the US, only about 1.2% of land is, on average, built out in this way. Everything else needs to be driven.

But here's the thing. Humans seem to really enjoy walkable urbanism, and will usually pay more for it:

City dwellers will pay to live in a walkable location. Real estate in these areas averages a 34% price premium per square foot in for-sale housing and 41% for multifamily rental apartments.

It also, by definition, punches above its weight:

Walkable neighborhoods in just those 35 metro areas account for 19.1% of the total US real GDP and 6.8% of the total US population, by the researchers’ calculations.

That's how density works. You get to do more, with less.

At the same time, not every place should be Midtown Manhattan (which the report labels as the highest walkable urban place with a floor area ratio of 40). There are a wide range of densities that will work, including modest ones (FARs between 1-3).

Here in Toronto, many of our single-family home neighborhoods have densities that are zoned for a maximum FAR of 0.6, which is quite restrictive if you're hoping to build something like a multi-unit building.

This is, of course, the point. But imagine what all could be done here with even an incremental change.

Here is an interesting set of maps (from this study) showing density trends, population trends, and residential area trends (i.e. sprawl), across Europe between 2006-2012 and 2012-2018:

The key takeaway is that, broadly speaking, there is -- or at least there was five years ago -- a new density trend across most European cities. From 2006 to 2012, the prevailing trend was de-densification. That is, fewer people per hectare. However, from 2012 to 2018, that trend largely reversed. With the exception of the Iberian Peninsula and Eastern Europe, the majority of cities flipped to densification.

The study tells us that there are two main reasons for this switch. The first is that more cities started growing again. During the first period, about 60% of cities in the sample size of 300+ cities, were adding people. In the second period, this figure increased to 75%. It's also worth noting that this growth is being largely driven by immigration, and increasingly so. The number of cities with positive natural growth diminished from 67% to 51% between the two study periods.

The second driver is a reduction in sprawl. Though almost every city in the study continued to expand outward, the rate of expansion was much lower between 2012 and 2018. So less land consumption, and more people. That's how you increase your urban density. Of course, it would be interesting to see if any of this has changed or reversed (again) as a result of the pandemic. 2018 kind of feels like eons ago, doesn't it?