CSIR’s statistical model came very close to predicting poll results

PRETORIA: Through its statistical model the Council for Scientific and Industrial Research (CSIR) accurately predicted the 2016 local elections’ outcome.

The predictions, made by means of analysis of statistical data, proved to be accurate and very close to the final results.

CSIR analyst Hans Ittmann explained that as soon as the results start coming in, they use that information to forecast how the rest of the people would vote.

The CSIR can already start their predictions once 5% of the counting process has happened, said Ittmann.

The predictions were based on a very specific model developed especially for the 2016 municipal elections.

The statistical methodology on which the predictions were based was called statistical clustering.

CSIR principal researcher Peter Schmitz said they divided the voting population into a number of groups.

He said they used about 20 clusters, where each cluster consisted of more or less the same kind of people with the same behaviour pattern.

Schmitz said that the first predictions came through between 4pm and 5pm on Thursday, August 4, and were reasonably accurate.

“At this stage, only 5 to 10% of voting districts had declared their results, although there were large parts of the country where no votes had come through at all.”

He maintained they were able to predict that the ANC would lose sole control of certain metros, namely Johannesburg, Tshwane, Ekurhuleni and Nelson Mandela Bay.

“We were also accurate in predicting that the DA would be the largest party in Nelson Mandela Bay, but not have an outright majority.”

In general the model performed extremely well and from an early stage the CSIR was able to identify major trends and the overall results of the election, said Schmitz.

He said they were able to predict the inversion of the current state in Johannesburg, where the DA was in a comfortable lead.

He said their prediction was close to accurate in Tshwane and Ekurhuleni, where the DA was at 50%, “and we came within a percentage point of predicting the final ANC tally of 48.9%”.

In Nelson Mandela Bay, the CSIR came within 1.8 percentage points of the final tally of 46.6%, he said.

Schmitz confirmed they were able to call the general result of no overall winner in these four metros.

“Finally, with absolutely no information available, our prediction for eThekwini was remarkably accurate.”

The experts working on the CSIR predictions consisted of experienced mathematicians, engineers and computer scientists.