SABC News partners with the Council for Scientific and Industrial Research (CSIR) to provide television, radio and online news consumers in South Africa a reliable prediction of the outcomes of elections. The SABC and the CSIR have done this since 1999.
The prediction model is designed to pick up changes in voting patterns in an election from a small number of voting districts (VDs), and therefore it can predict very soon after results start coming in what the final pattern is going to look like.
The model uses statistical methods to group VDs into clusters (or groups) that vote in a similar way (this is done before the elections). Then, when results are received from a particular VD from the IEC, those results can be translated into results for the entire cluster of that VD.
With just a small number of VD results (for example, 10% or roughly 2300 VDs) one can therefore estimate results for the entire cluster and the clusters results can then be combined to an overall total result.
As more and more VD results come in the totals from the clusters are eventually just the actual totals.
The CSIR model only uses results from VDs, and no additional polling or surveys are done by the CSIR.