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:

Garrett Dash Nelson recently published a study looking at urban density on a cell-by-cell basis for a number of US cities. Each "cell" is a 30 arc-second grid cell, but you can think of them as being approximately one square kilometer. The goal of the project was to better define urban density and do it in a more granular way. City averages don't tell you a whole lot about how neighborhoods vary, and they can be skewed by the denominator you use. i.e. Where are you drawing the urban boundary?

You can play around with his interactive study, here. Each city can be explored according to its 200 most dense cells. One interesting takeaway -- though it is probably not all that surprising to this audience -- is that New York City is really a unique place when it comes to American cities. If you look at the above chart (sourced from CityLab), you'll see that most other US cities don't come close to it in terms of urban density. New York's 200th densest cell is still denser than the most dense cells of Boston, the Twin Cities, and of Dallas.

The y-axis is the total population in each grid cell.