Scottish Referendum – Prediction on 17th of September

This is a Forward Looking prediction. This means it is a forecast of what the Yes vote will be on the 18th of September.

The Forward Looking “centre point” of the prediction is 47.60%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data. This prediction is down almost 1% from yesterday.

The Point in Time “Probability of Yes being greater than 50%” prediction is 3.07%.  This means that when we run 10,000 simulations of the referendum based on current polling trends and the variances within them, Yes would win only 307 times. This prediction is down over 25% from yesterday.

The table below shows the 50% and 95% confidence intervals for the Yes vote.

Date Yes% 50% Intervals 95% Intervals
11th September 48.18 47.14 – 49.23 45.15 – 51.21
12th September 47.82 46.76 – 48.88 44.74 – 50.91
13th September 47.40 46.16 – 48.64 43.80 – 51.00
14th September 48.95 47.60 – 50.31 45.02 – 52.89
15th September 48.36 47.26 – 49.46 45.15 – 51.57
16th September 48.50 47.08 – 49.93 44.36 – 52.65
17th September 47.60 46.96 – 48.14 45.84 – 49.26

Why has the probability of a Yes win dropped so dramatically?

Last night’s three polls were remarkably similar. Even though all three were reported as 48% Yes, the levels for all three are actually around 47.7%. This similarity allows us to have much more confidence that the true figure for public support is very close to this value, reducing the size of the confidence intervals of the prediction.

Where do you see the Yes vote moving by Thursday?

We still have some more polls to come out this evening and they will either confirm the move away from Yes (which is now statistically significant, helping to move our forecast even further towards a No vote) or they will indicate a last minute change in sentiment, boosting the chances of a Yes vote.

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