Scottish Referendum – Eve of Count Forecast

This forecast takes account of the final MORI poll for the Evening Standard.

This is an Election Day prediction. This means it is a forecast on the day of the Election as to what the actual Yes vote will be.

The Election Day “centre point” of the prediction is 47.90%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data.

The Election Day “Probability of Yes being greater than 50%” prediction is 4.01%.  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 401 times.

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
18th September am 47.78 47.28 – 48.28 46.32 – 49.24
18th September pm 47.90 47.45 – 48.36 46.58 – 49.22

Is this your final prediction? 

Yes. We now have all the data tables from all the polls. There is nothing left to do now but find out the result.

What is the main feature of the last few days of polling?

Undoubtedly the main observation has been the narrowing of the confidence intervals of our prediction. With so many polling firms delivering results in the same area, it is clear that the margin of error has contracted significantly and this has contributed to the reduction in the probability of a Yes victory. If you compare our prediction this morning to those on the 13th, today we have a higher centre point but much shorter confidence intervals.

What if your prediction is wrong?

If our prediction is wrong then all the polling firms are wrong. Given that there has never been a referendum in Scotland on this issue before, weightings and accounting for those who previously haven’t voted may be compromised. However, in the absence of any empirical evidence that the polls are biased, we must treat them as unbiased barometers of public opinion.

Scottish Referendum – Prediction on Morning of Vote – Adjusted for MORI

This forecast has been adjusted to account for the new MORI poll for the Evening Standard. It incorporates the headline figures from this poll and will be adjusted again once the data tables are published.

This is an Election Day prediction. This means it is a forecast on the day of the Election as to what the actual Yes vote will be.

The Election Day “centre point” of the prediction is 47.78%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data.

The Election Day “Probability of Yes being greater than 50%” prediction is 3.22%.  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 322 times.

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
18th September 47.78 47.28 – 48.28 46.32 – 49.24

Is this your final prediction? 

Potentially not. There may be another poll out today in the English press and if that is released we will update our forecast accordingly.

What is the main feature of the last few days of polling?

Undoubtedly the main observation has been the narrowing of the confidence intervals of our prediction. With so many polling firms delivering results in the same area, it is clear that the margin of error has contracted significantly and this has contributed to the reduction in the probability of a Yes victory. If you compare our prediction this morning to those on the 13th, today we have a higher centre point but much shorter confidence intervals.

What if your prediction is wrong?

If our prediction is wrong then all the polling firms are wrong. Given that there has never been a referendum in Scotland on this issue before, weightings and accounting for those who previously haven’t voted may be compromised. However, in the absence of any empirical evidence that the polls are biased, we must treat them as unbiased barometers of public opinion.

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.

Scottish Referendum – Prediction on 16th 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 Point in Time “centre point” of the prediction is 48.50%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data. This prediction is up almost 0.15% from yesterday.

The Point in Time “Probability of Yes being greater than 50%” prediction is 28.37%.  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 2,837 times. This prediction is up over 4% 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

Why has your prediction changed when there have been no new polls?

Our prediction takes into account the age of the polls. As the time between the original fieldwork of a poll and today increases, the reliability of the poll in telling us what sentiment is like right now decreases. This uncertainty is reflected in the widening confidence intervals and the shift in the centre point of the Yes vote distribution prediction.

Where do you see the Yes vote moving by Thursday?

At the moment the trend continues to be broadly flat. Our forecast has moved to the Yes = 48.5% mark, but this may change very rapidly if new polling data indicates a move in public opinion.

Scottish Referendum – Prediction on 15th 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 Point in Time “centre point” of the prediction is 48.36%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data. This prediction is down 0.6% from yesterday.

The Point in Time “Probability of Yes being greater than 50%” prediction is 24.08%.  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 2,408  times. This prediction is down 10% 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

Why has your prediction for the Yes vote gone down when there are no new polls?

We have now been able to look in greater detail at some of the polls published at the weekend. This allows us to clarify our forecasts and firm up on the general trend in the polls.

Where do you see the polls going in the next four days?

At the moment the trend is broadly flat with a slight, but statistically insignificant move away from Yes. If this trend continues we should expect to see polls oscillate around the Yes = 48.5% mark.

If we see the trend move away from this 48.5% mark we will flag it up for you accordingly.

Scottish Referendum – Prediction on 14th 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 Point in Time “centre point” of the prediction is 48.95%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data. This prediction is up over 1.5% from yesterday.

The Point in Time “Probability of Yes being greater than 50%” prediction is 34.66%.  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 3,466  times. This prediction is up almost 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

Why the large movement today?

We take into account not just the most recent opinion polls but also the overall trajectory in recent days. Last night’s polls indicate that there is a movement back in support towards “Yes”.

We have not seen the data-tables yet for the ICM and Panelbase polls, so when the available data from these polls is richer our forecast my adjust further.

What about that large ICM Yes lead yesterday?

The ICM poll overnight was one of four, and the only one to show a Yes lead. It was also a different sample methodology than previous ICM polls, and a smaller size (700).

Our analysis shows that the ICM poll is right at the upper end of where we believe the true Yes figure currently lies. It is what we call “an outlier”.

Scottish Referendum – Prediction on 13th of September

Please note – this is no longer a point in time forecast but rather now a forward looking forecast for the 18th 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 Point in Time “centre point” of the prediction is 47.40%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data. This prediction is down 0.42% from yesterday.

The Point in Time “Probability of Yes being greater than 50%” prediction is 10.73%.  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 1,073  times. This prediction is down over 0.75% 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

Why is your prediction lower than most recent polls?

We take into account not just the most recent opinion polls but also the overall trajectory in recent days. At the moment the polls are indicating that there is a downward movement in support for “Yes”.

If there are more polls that show a rise in sentiment for “Yes” then our prediction may move up again.

Scottish Referendum – Prediction on 12th of September

Please note – this is no longer a point in time forecast but rather now a forward looking forecast for the 18th 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 Point in Time “centre point” of the prediction is 47.82%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data.

The Point in Time “Probability of Yes being greater than 50%” prediction is 11.55%.  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 1,155  times.

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

Why is this Forecast so different from the one posted yesterday?

Yesterday’s forecast was a “Point in Time” forecast indicating what the position would be if the vote had happened yesterday. With 7 days to go to the referendum we have now switched to an 18th of September forecast.

Scottish Referendum – Point in Time Prediction on 11th of September

This is a Point in Time prediction. This means it is a forecast of what the Yes vote would be if the referendum happened today.

The Point in Time “centre point” of the prediction is 49.37%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data. This is a movement of 0.4% down from yesterday’s prediction and represents a strong move away from an actual Yes victory.

The Point in Time “Probability of Yes being greater than 50%” prediction is 35.63%.  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 3,563  times.

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

Date Yes% 50% Intervals 95% Intervals
8th September 49.46 47.60 – 51.32 45.74 – 53.18
9th September 49.51 48.00 – 51.01 46.94 – 52.52
10th September 49.76 48.26 – 51.27 46.75 – 52.78
11th September 49.37 47.65 – 51.08 45.94 – 52.80

There are currently too few data items to produce an 18th of September Forecast.

Scottish Referendum – Point in Time Prediction on 10th of September

This is a Point in Time prediction. This means it is a forecast of what the Yes vote would be if the referendum happened today.

The Point in Time “centre point” of the prediction is 49.76%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data. This is a movement of 0.25% upwards from yesterday’s prediction and represents a strong move towards an actual Yes victory.

The Point in Time “Probability of Yes being greater than 50%” prediction is 43.78%.  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 4,378 times. This is a movement of over 6.5% up from yesterday’s prediction.

There are currently too few data items to produce an 18th of September Forecast.