Population Ratios of Top Three Urban Agglomerations

Some countries have a single large urban agglomeration that is much bigger than other urban areas in the country. Others have three or more major agglomerations that are pretty close in size.

For a while I've wanted to visualize different countries depending on whether they were more like the former or more like the latter.

So I took some data from http://www.citypopulation.de/ and used HTML Canvas to create a bubble plot of all countries with three or more agglomerations over one million people. I used the ratio of the population of the largest agglomeration and the second largest as the y coordinate and the ratio of the population of the second largest and the third largest as the x coordinate.

Here is the result:

Population Ratios of Top Three Urban Agglomerations

Besides this criterion, I can't immediately think of other similarities Argentina, the Philippines, France or South Korea have; or India, China, Italy and the Netherlands; or Russia and Bangladesh.