The following diagrams were taken from LSE’s Urban Age website. I’ve sorted them from lowest to highest peak residential population density. In each case I’ve also included the year of the dataset. 

It’s amazing how much these simple extrusion diagrams can tell you about the city. It also shows you that high population densities don’t necessarily need to equate to tall buildings. Barcelona, in particular, stands out for me.

Berlin (Peak residential density: 21,700 people/km2, 2009)

Stockholm (Peak residential density: 24,900 people/km2, 2012)

London (Peak residential density: 27,100 people/km2, 2013)

São Paulo (Peak residential density: 29,380 people/km2, 2009)

Mexico City (Peak residential density: 48,300 people/km2, 2009)

Barcelona (Peak residential density: 56,800 people/km2, 2013)

New York (Peak residential density: 59,150 people/km2, 2012)

Shanghai (Peak residential density: 74,370 people/km2, 2011)

Istanbul (Peak residential density: 77,300 people/km2, 2013)

Hong Kong (Peak residential density: 111,100 people/km2, 2013)

Mumbai (Peak residential density: 121,300 people/km2, 2013)

The 2015 edition of The Global Financial Centres Index (GFCI) was just released last month. It is often used as one of the sources for ranking financial centres.

The index – which is now in its 18th edition – is created using two main ingredients. The first is an analysis of 5 broad areas of competitiveness: 1) business environment, 2) financial sector development, 3) infrastructure, 4) human capital, and 5) reputational & general factors. And the second is an online survey given to financial services professionals. The 2015 edition includes responses from 3,194 professionals.

Below are the top 25 financial centres in the world according to the GFCI (the full list has 84 cities).

Here are a couple of things to note from this year’s index: 

London has overtaken New York for the top spot – but both remain more or less at parity if you dig into the numbers. 

Dublin is performing particularly well in Western Europe.

The leading centre in Eastern Europe is Warsaw (38th), with Istanbul just behind it.

Toronto is now second in North America, only to New York.

Sao Paulo remains the top Latin American centre.

And, Los Angeles (49th) and Liechtenstein (60th) join as new entrants this year.

If you’d like to see the full report and ranking, click 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.