Further Analysis of Betting Odds for Scottish Independence Referendum

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Fotolia_64516645_SWith just one day to go to the vote, this analysis outlines the current odds, and may give some pointers to the outcome. The data used in this analysis looks back at the daily odds for a Yes vote from 23 bookmakers over the last five months (1 April – 17 September 2014).

Even in the day before the vote, there is a great deal of change with the average decimal odds for a Yes Vote at 4.3, and which has drifted out from 3.91 (16 September 2014). There’s a bit of movement that isn’t quite consistent, as 14 have odds which are lengthening for a No vote, and six with odds reducing. For the Yes vote with odds sit at 1.22 which has drifted in from 1.28 (16 September 2014). A typical vote is 1.22 (2/9) for No and 4 (3/1) for Yes. So at this point there is still a fairly wide gap in the odds.

Figure 1 outlines the odds for the past five months. It can be see that the odds for a No vote are approximately where they started off with at the start of May 2014, with a large drift out at the start of September 2014, but drifted back in over the last few weeks.

Figure 1: Odds on a Yes vote (using decimal odds)

Outline of odds

In the independence poll, there are only two horses in the race, so there is either a Yes or a No bet. The way that odds are normally defined is the fraction which defines the return, so Evens is 1/1, where for every £1 bet, you will get £1 back in addition to your stake (so you get £2). If the odds are 2/1 (2-to-1 against), you get £2 back plus your stake (so will get £3 on a win). For 1/2 (or 2-to-1 on), you get half your money back, and you’ll get £1.50 on a win. These types of odds are known as fractional odds, where the value defines the fraction for your payback. The multiplier, though, does not show your stake coming back to you, so decimal odds are used to represent this, and defines a value which is multiplied to the stake to give the winning amount (basically just the fractional odds plus 1, and then represented as a decimal value).

The factional odds value of Evens gives a decimal odds value of 2 (where you get £2 back for a £1 stake), and 2/1 (2-to-1 against) gives 3.0, while 1/2 (2-to-1 on) is 1.5. In terms of roulette, Evens would define the odds for a bet of Red against Black (as each are equally probable). In roulette, though, the odds are slightly biased against the player for a Red v Black bet, as 0 changes the odds in favour of the casino. For betting, overall, bookmakers try to analyse the correct odds so that they have attractive ones (if they want to take the best), against others. If they take too much of a risk, they will lose, so their odds around the independence vote should be fairly representatives of the demand around bets, and the current sentiment around the debate.

Percentage share of the vote and turnout

Figure 1 outlines the decimal odds for the Yes vote, and it perhaps reflects the closeness of the vote, with an Evens money bet for a share between 45 and 50%, with 3.5 for 40% to 45% and 5.1 for 50% to 55%:

40% or less 6.8
40 to 45%    3.5
45 – 50%     2.1 (approx Evens).
50 – 55%     5.1

In terms of the turnout, the favourites are over 85% and between 80 and 85%:

Over 85%  2.62
80 – 85%    3
75 – 80%    3.5
70 – 75%    5.5
65 – 70%    17

chart04Figure 1: Percentage share for Yes vote (17 Sept 2014)

The Trend

The trend for the last 30 days is shown in Figure 3. The key turn-around in the odds for the No vote happened after 22 August, where the odds were as high as 6.27. They generally slipped over the weeks after that hitting a plateau around 7 Sept until 10 Sept 2014 (down to 2.78), and rose back up to 4.39 over the next four days, and have started to come back down over the past four days. The past day, though, has seen them rise again, perhaps outlining the small lead in the polls for a No vote.

Figure 3: Yes odds for the past 30 days

Figure 4 shows the variation of the odds over the 30 days for the Yes vote odds, and highlights the drift out of the Yes vote around 8 Sept 2014.

Figure 4: Yes Vote odds for 23 bookmakers over August 2014

Geographical trends

In terms of voting for the place that is most likely to have the strongest Yes vote, Dundee has been out in-front for many months, with current odds of them having the largest Yes vote at 1.5 (1/2), and quite a long way in front of the Clackmannanshire (5/1) and Glasgow (8/1). Table 1 outlines the split of the Top 10 most likely to vote Yes (in terms of betting odds), and the Top 10 least likely to vote Yes. Of the areas which are the strongest, it is difficult to generalise, but the Highland areas, and the West of Scotland are strongest, whereas the South of Scotland, East of Scotland, and the Northern Isles the least likely (based on the odds).

Overall the major polulation areas on the east coast of Scotland, apart from Dundee, are generally in the bottom half of the geographical split, with Edinburgh (23th out of 32) and Aberdeen (19th out of 32):

  • Dundee (1st out of 32).
  • Glasgow (3rd out of 32).
  • Stirling (12th of 32).
  • Perth (17th out of 32).
  • Aberdeen (19th out of 32).
  • Inverness (22nd out of 32).
  • Edinburgh (23rd out of 32).

Table 1: Geographical split on most likely to have the strongest (and weakest) Yes vote

Top 10 to Vote Yes Top 10 least like to vote Yes
1. Dundee (most likely) 23. Edinburgh
Clackmannanshire Renfrewshire
Glasgow East Lothian
Na h-Eileanan Siar Orkney
Angus Shetland
Moray Scottish Borders
East Ayrshire East Dunbartonshire
Falkirk East Renfrewshire
Aberdeenshire South Ayrshire
10. Highland 32. Dumfries and Galloway (least likely)

The key changes

A key change took place around the 5 August debate, where the odds for a Yes vote odds had been dropping before the debate, but after it, the average odds for a Yes Vote moved steeply up (dropping one point in the days before the debate, and then rising 1.2, for four days after it):

9 Aug 5.75
8 Aug 5.43
7 Aug 5.05
6 Aug 5.05
5 Aug 4.54
4 Aug 4.39
3 Aug 5.5

On the day before the second debate there was a peak Yes Vote odds of 6.3 (22 August 2014), and this has since fallen to nearly 4 ( 31 August 2014). The largest changes in the odds have thus occurred around the debate points, with 5 August 2014 having 31 changes (where general the No vote odds have drifted out) and 9 changes on 23 August 2014. Also, typically, there is an increasing rate of change of the odds as we move closer to the vote.


There is a strange dynamic going on in the betting market, as the polls are saying it is close, but the bookmarkers are not reflecting that. Overall there’s only one thing that really matters, and that is the vote tomorrow, and opinion polls and bookmarker odds can only make best guess on a generalised feeling of the nation. For this vote, may perhaps show a new dynamic, where it is difficult to generalise feelings and analysis purely by opinion polls or general sentiment. It has been a vote which most of the printed media outlets have backed the No campaign, but, in these days of social media, they are not necessarily the main outlets for information.

Key observations:

  • Some bookmakers, especially the spread betting ones have rapid changes in odds, while other are static (with one bookmaker making changes in the odds one a month).
  • The largest number of changes in a single day, over the past five months, was 31 and occurred on 5 August 2014, which was the date of the debate between Alex Salmond and Alistair Darling.
  • Dundee, Glasgow and Clackmannanshire come out way in-front for the place most likely to vote Yes, with Dumfries and Galloway the least.
  • The odds are erring on the side of a Yes vote from 45% to 50%.

One disappointing factor is that Betfair has already started to pay-out on a No vote, as they reckon it is 78% certain (which in no way is even nearly a certainty). In fact, that’s the odds of not pulling out the Ace of Spades from four cards holding each of the aces. In one in four turns we will pull-out the ace of spades. So I do maths and not politics, but I do understand that 78% is nowhere near certain.

Well only tomorrow will actually define what really has happened … the bookmakers and punters can only speculate.

Note: This is a non-political analysis, and is purely focused on analysing open-source data related to bookmaker odds. It is inspired by the usage of big data analysis, and how this identifies trends.

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