It's not always as straightforward as it may seem to measure the size of a city or urban region.

There's the problem of which urban boundary to use. And then once you've landed on that, there's the additional problem of estimating how many people live within it. This can be particularly challenging when it comes to informal settlements, where there isn't reliable population data.

The most common approach is to use the continuous built-up area as the urban agglomeration, as opposed to any sort of "city proper" boundaries. And this is exactly what the United Nations has done in its latest World Urbanization Prospects report.

Here, they have fundamentally revised their measurement methodology by using a new, so-called harmonized geospatial approach. If you'd like to nerd out on the specifics, you can do that here.

But one of the key takeaways is that this new methodology has resulted in a reordering of the world's largest urban agglomerations. At the top is now Jakarta, followed by Dhaka:

It's not always as straightforward as it may seem to measure the size of a city or urban region.

There's the problem of which urban boundary to use. And then once you've landed on that, there's the additional problem of estimating how many people live within it. This can be particularly challenging when it comes to informal settlements, where there isn't reliable population data.

The most common approach is to use the continuous built-up area as the urban agglomeration, as opposed to any sort of "city proper" boundaries. And this is exactly what the United Nations has done in its latest World Urbanization Prospects report.

Here, they have fundamentally revised their measurement methodology by using a new, so-called harmonized geospatial approach. If you'd like to nerd out on the specifics, you can do that here.

But one of the key takeaways is that this new methodology has resulted in a reordering of the world's largest urban agglomerations. At the top is now Jakarta, followed by Dhaka: