Accuracy of CSDS Exit Poll Predictions
CSDS is one of the oldest practitioners of exit polls. They call it a post poll survey and the National Election Study is now about 50 years old. The NES delivers a lot of insights that goes beyond seat predictions. However, today we shall focus on recent accuracy of exit polls carried out by CSDS. We will consider the post 2014 General election period to be fair on recency.
We considered a total of 6 elections. That is because CSDS has not done as many exit polls when compared to the past. To be specific, we are focussed on seat estimates only. The 6 States where Seat Forecasts were put out using CSDS data (usually by Chennai Institute of Mathematics) are Madhya Pradesh, Gujarat, Uttar Pradesh, Punjab, Chhattisgarh and Rajasthan.
Accuracy of predicting seats for BJP
In the 6 States considered,
Error was below 10% in zero cases
Error was between 10 and 20% in 3 cases
Above 20% in 2 cases
The average error was 65.6%. Excluding Chhattisgarh, the average error is 29%
CSDS over reported BJP’s seats in four out of 6 cases
Accuracy of predicting seats for Congress
Please note that UP includes SP and Congress
Error was below 10% in one case
Error was between 10 and 20% in one cases
Above 20% in 4 cases
The average error was 52.9%. Excluding UP, the average error is 23.2%
CSDS over reported Congress party’s seats in three out of 6 cases
Overall, CSDS’s best prediction was in Rajasthan followed by Gujarat and Madhya Pradesh. As a thumb rule, an error of 10 to 20% for the projected winner might work out in general.