The Toilet Map Done in a (Slightly) Different Way

Thanks very much for all the positive comments on the toilet map in the previous post. But one thing bothered me about it and I thought I would fix that.

The issue comes up whenever you use maps to represent social or economic data and it has to do with the rather obvious fact that maps represent parts of the surface area of the earth.

Take the case of Ladakh and Mumbai. In the previous map, Ladakh (represented by the big area right at the top) has a very small population but relatively large surface area. Mumbai is exactly the opposite. So Mumbai, with around 20 million residents, shows up as a small speck on the map, but Ladakh with a population nowhere close to that of Mumbai’s, shows up as the biggest part of the map. Visually, Ladakh dominates, because it covers a huge area, though in terms of the size of its poulation (which is more relevant when we are talking about toilets or cellphones or whatever), it really shouldn’t. The tehsil of Jaisalmer in the far west of the country is another example – large surface area but relatively sparsely populated.

Geographers have of course known this problem for long, and have tried various ways to fix it.  The map below is one way to do so. Each tehsil is now just a dot of the same size on the map, irrespective of area. Now, no district is more obvious than any other, purely by virtue of the fact that it covers a bigger area. I also changed the colour scheme just for the heck of it. Everything else is unchanged.

(Apologies but this post may take a while to load on a slow connection, and/or if you are using a tablet or phone. Click or tap on the map to switch between 2001 and 2011. Hover your mouse over a tehsil to see its details. The greyed-out regions are those for whom data couldn’t be compiled, or those which are not relevant e.g. PoK)

There are still other problems  – the eye seems naturally drawn to Bihar, West Bengal and northern Andhra purely because the tehsils there are much smaller. So the dots cluster much more closely together giving rise to a continuous band of colour in those regions. But on the whole, I think this is a better way to do it.

Edited to add: Even this map is a second best solution. What I should do is size each dot to reflect population density in that area. So for instance, Mumbai would show up as a larger circle than Jaisalmer or Ladakh. But the technical challenge of creating such ‘cartograms’ are beyond me at this stage.

Thanks to a reader who pointed out that the ‘tooltips’ – which show details of each area when you hover the mouse over them – don’t work in Firefox browsers for some reason. I have no clue why. I’m working on it, but in the meanwhile, you are probably better off using Chrome. Sorry about that.

Notes :

Please see the previous post for the full set of notes. Map created using the D3 javascript library and colours are from colorbrewer.

September 14, 2013

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