The linguistic diversity index measures the probability that two people selected at random from a population speak different home languages. The map below, which I produced, depicts the linguistic diversity index calculated on a 10-kilometre-wide hexagonal grid across South Africa.

I’ve made an interactive website with six sets of topographic maps of Cape Town and surrounds covering the period from 1940 to 2010. You can zoom in and move around the maps, switching from one era to another.

The post-apartheid political map of South Africa might well have looked quite different. The Eastern Cape might have been divided into two provinces, with the Kat River and Great Fish River on the boundary. The Northern Cape might not have existed, with the Western Cape meeting North West at the Orange River. Gauteng might have been much bigger – or much smaller. The Western Cape might have stopped south of Citrusdal – or it might have incorporated all of Namaqualand.

After the recent US Supreme Court ruling legalising same-sex marriage (SSM) throughout that country, a claim was recently brought up on a Wikipedia talk page that more than one billion people now live in countries (or states/provinces) where SSM is legal. I thought I’d check out the numbers, and update my old graph showing how this has changed over time.

As “the data guy” for the Democratic Alliance, naturally my job involves working with election result data. This post is a collection of mildly interesting facts I’ve learned about the 2014 elections in the course of my work. I’ll start off with a quite surprising fact: the location of the busiest voting station.

My post yesterday discussed the mean centres of population of South Africa and its provinces. The mean centre is (relatively) easy to calculate, but it may not be the most useful type of population centre. It is essentially an arithmetic mean, which means that outliers can have a massive effect on the centre. It minimizes the average square of distance from the centre, not the average distance from the centre. The centre that does minimize the average distance is called the geometric median, and it is not quite so simple to calculate, since there is no closed form solution. But it can be done!

Follow-up: a subsequent post describes the geometric median centre of population, which is some respects a more sensible definition than the mean centre of population described here.

At some point in school, we South Africans are told that the official decimal separator is the comma.¹ Most of us then proceed to ignore this—at least in English use²—because it differs from the decimal point used in the rest of the English-speaking world, and thereby creates confusion. Thankfully, the maintainers of the glibc locale data—and thus the number formats used in Linux systems—agree with me on this question, and the South African English locale uses the decimal point.

Ever wondered where that (Western Cape registered) car is from? Wonder no more: (you can click on the map to see a bigger version)

I’ve drawn some maps showing the percentage-point change between the 2009 and 2014 elections in the vote share of the major parties (or, in the case of COPE, formerly major parties). Because municipal boundaries have changed a bit, I had to recalculate the 2009 results for the 2014 boundaries, by assigning the voting districts from 2009 to wards from 2014. In the cases where a 2009 VD was spread across multiple 2014 municipalities, I assigned it according to the location of the voting station.