I'd rather be happy than right: 2015 personal election review

Well that didn't go as expected.  With the luminous exception of Scotland, I was completely wrongfooted by how the election result turned out.  I could argue that so was everyone else but that would be a bit of a cop out.  It's my turn to eat some humble pie.

So what did I get right and what did I royally mess up?  The best place to start must be my end of year predictions:

http://newstonoone.blogspot.co.uk/2014/12/2015-may-and-everything-after.html

These were, in order:

1. There would be a hung Parliament
2. It will be neck and neck between the Lib Dems and the SNP which would be the third party.
3. UKIP would get a good poll rating and few seats to show for it.
4. The Greens would take precisely one seat: Brighton Pavilion.
5. The debates would take place, basically in the format put forward by David Cameron.
6. The election campaign wouldn't change very much.
7. There would be a Labour minority government.
8. All of the leaders (except Nicola Sturgeon) would be in peril of losing their jobs.

Not good, are they?  I was right about UKIP and the Greens, half right about the debates (the format changed considerably) and right about the pressure on the leaders apart from David Cameron - though Nigel Farage's bouncing resignation was an innovation in British politics that I hadn't expected.  But for the rest, I was hopelessly wrong. 

There's no point sugaring the pill, this was a terrible set of predictions.  What went wrong?

Despite being very aware that polling was an unreliable friend and likely to be particularly unreliable this time with the rise of UKIP and the SNP and the crash of the Lib Dems, I still relied heavily on the opinion polls.  I think I acted correctly when I put together these predictions - you have to make use of the evidence that you have got in the absence of concrete reasons to doubt that evidence.  At the turn of the year, I had no such concrete reasons.

In fact, my year-end predictions were largely what I expected right up to 10pm on 7 May 2015 (but by that stage I expected the SNP to far outstrip the Lib Dems, though even then not by as much as in fact happened).  The polls had remained static, even though the mood music from both main parties and the campaign itineraries of the two main party leaders suggested something different from the polls.  That failure to revise my expectations was less forgivable.  Ed Miliband would not have been campaigning in North Warwickshire and David Cameron would not have been campaigning in Twickenham and Bath if they didn't believe that the election was far adrift of where the polls suggested.  One of them might have been wrong.  Both of them were most unlikely to be.  I should have taken more notice.

So I wasn't right.  But I am still happy.  Why?  Because my betting produced the returns I was looking for from them.  How did I turn a profit when I had been such a poor prophet?  I need to break this down into asset allocation, stock selection and timing.

As of 10pm on Thursday night, my portfolio of fixed price bets was comprised in the following categories:

1. Scottish constituency bets, almost all on the SNP
2. English constituency bets, the great majority on the Conservatives, but not exclusively if I saw bets that I thought offered disproportionate value on other parties
3. Hung parliament (I'll come back to this)
4. Labour most seats
5. Labour minority government
6. Laying David Cameron as Prime Minister after the election and backing Ed Miliband as Prime Minister after the next election
7. Miscellaneous others

I had placed some spread bets, but this time I didn't put huge sums at stake that way.  My focus was elsewhere.

You can see from the bets that I placed that these were partly indirectly hedging.  Relative longshot Conservative constituency bets were inconsistent with bets in categories 4, 5 and 6 in particular.  By selecting constituency bets that I felt were likely to outperform each party's run-of-the-mill seats for the same odds, I hoped to maximise returns.

I did so well on my Scottish constituency bets that everything else pales into insignificance.  They comprised roughly 80% of my winnings.  This was a triumph of asset allocation - all those hours I spent poring over the likeliest SNP wins proved entirely superfluous in the end (indeed, at an early stage I had managed to back the SNP to win Edinburgh South, the one seat that they did not take, though having obtained odds of 25/1 on that possibility I can scarcely be too upset).

But I did OK elsewhere also.  On Thursday morning, I thought that most of my English constituency bets on the Conservatives were heading for the virtual ashtray.  But on Friday morning, they largely came up trumps.  My strategy of seeking out value on both sides of the fence left me ahead.  Here, stock selection was more important.  And I did OK, particularly as regards the battle between Labour and the Conservatives.  

Labour took ten seats from the Conservatives.  Of these, I had placed losing bets on the Conservatives holding City of Chester, Hove and Ilford North.  But conversely I did bet on Labour taking Brentford & Isleworth and Ealing Central & Acton.  I avoided betting on the other five either way.  Meanwhile, I successfully backed the Conservatives (at fairly long odds) to keep many of their other most marginal seats, and while I'd backed Labour to take some other seats, I am not embarrassed by my choices there either.  Taken as a whole, I think I did a pretty fair job of identifying which Conservative seats might underperform and where Labour might outperform against the Conservatives.

In other battlefields, the story was much closer to neutral overall (I did conspicuously badly with UKIP).  But I did best where I'd bet most.  

I made one other critical decision early on Friday morning which was worth a four figure sum to me.  After seeing the exit poll, I was aware that it was in doubt whether the Conservatives would merely be the largest party or whether they might get an overall majority.  Following the results in Nuneaton and Swindon North, where the Conservatives had outperformed the exit poll in each case, I reversed my previous position on no overall majority and backed the Conservatives getting an overall majority at fairly long odds.  Timing was everything on this. 

If this all sounds too smug, please return to the top and reread my serving of humble pie.  I will.  Overall, I made a complete hash of my predictions.  Fortunately, I got away with it.  This time.

When April turns to May: what the seat markets imply for the election result

It's time to put the pieces together.  Over the last few days, I've been looking at the constituency markets on a party by party basis, sorting the seats by the implied probability that the bookies have given to each party in turn and looking at what that means for them both in general terms and in specific seats.  I attach links to each of them below (some of the prices are already slightly out of date, particularly following the gyrations in the prices in the Scottish constituencies over the weekend):

Labour

http://newstonoone.blogspot.co.uk/2015/04/the-labour-battleground-in-april-2015.html

Conservatives 

http://newstonoone.blogspot.co.uk/2015/04/the-conservative-battleground-in-april.html

Lib Dem 

http://newstonoone.blogspot.co.uk/2015/04/the-lib-dem-battleground-in-april-2015.html

 SNP 

http://newstonoone.blogspot.co.uk/2015/04/the-snp-battleground-in-april-2015.html

UKIP 
 

http://newstonoone.blogspot.co.uk/2015/04/the-ukip-battleground-in-april-2015.html
 

Greens, Plaid Cymru, Respect, NHA and Independents

http://newstonoone.blogspot.co.uk/2015/04/other-parties-and-independents.html
 

And new for April, I've prepared tables for the Northern Ireland seats:

https://drive.google.com/file/d/0Bygi8eZw-4q1SXBsTVFWVVRJRmM/view?usp=sharing

I don't propose to give any commentary on the Northern Irish seats, partly because I have no great insight and partly because there aren't that many interesting seats.  Some of the DUP and Sinn Fein 1/100 bets are as sound 1/100 bets as you will find anywhere, mind.
 

Now it's time to put together the overall picture as it stands.

Projected seat tallies

What are the implied seat counts?  Allocating the seats to the favourites (halving them when there are joint favourites) gives the following seat counts:

Conservative: 273
Labour:265 1/2*

SNP: 54

Lib Dems: 30 1/2

DUP 9
Sinn Fein 5
SDLP 3
Plaid Cymru: 3
UKIP: 3
Speaker: 1

Lady Sylvia Hermon: 1
Greens: 1
Respect: 1

*This figure has been adjusted to take account of the intervening seat movements in Scotland since the Labour seat odds table was compiled.

What kind of government would that produce?  Labour plus SNP would be just shy of the magic 326 figure.  Adding in the support of the SDLP, Plaid Cymru, the Greens and Lady Sylvia Hermon and the passive support of Respect would get a Labour-led government control of Parliament.

That would work for UK-wide matters, but the SNP would not be reliable partners for English-only matters.  In those circumstances, Labour would probably need Lib Dem support also.

Nevertheless, the par numbers suggest a rickety Labour minority government.  If it panned out like that, it would be fun.  You can still get that at 7/4 and I've been tipping it since it was 7/1. 

 

What might yet change?

That's all well and good, but we need to think about what are the likely bounds of possibilities.  With less than three weeks to go we can largely confine ourselves to the 1/2 to 2/1 bands.  There will be seats won at longer odds, but we should now expect that to happen relatively rarely.

 

So what's the likely minimum and maximum for any party?  Here are the totals that each party would tally if they took all the seats in which they are priced at 1/2 or shorter (but no more) and the totals that each party would tally if they took all the seats in which they are priced at 2/1 or shorter (but no more):

Labour: 241* - 301*

Conservative: 239 - 305

SNP: 43 - 57
Lib Dems: 17 - 37

DUP: 9

Sinn Fein: 5
Plaid Cymru: 2-5
SDLP 2 - 3
UKIP: 1 - 7
Speaker: 1
Lady Sylvia Hermon: 1
Greens: 1
Respect: 0 - 1
UUP: 0 - 2

*This figure has been adjusted to take account of the intervening seat movements in Scotland since the Labour seat odds table was compiled.

What can we sensibly note?  Well, first, it is now most unlikely that we will see an overall majority.  You can back No Overall Majority at 1/8 on Betfair and that looks like value even at that price to me.  Note that before the latest SNP surge, Labour were priced at 2/1 or less in 322 seats, meaning that their outer bound was within a whisker of the overall majority threshold.  That has receded into the distance.   1/8 on No Overall Majority is some way too long.

 

Secondly, it is going to be very hard for the Conservatives to get to form the next government.  If they don't get an overall majority (or very close), they're going to need the connivance of the Lib Dems.  The Conservatives will need at least 295 seats and that is close to the top end of the range for them.  Laying David Cameron as Prime Minister after the next election looks value right the way to 2/1 at the least.

 

Oh, and the 7/4 on Labour minority government continues to look like very good value, particularly given that the SNP would be an essential component of any majority and there is no prospect of any coalition between those two parties.

But I've plugged all these bets before.  Do I have any new ones?

 

These ranges are surprisingly tight.  You could take the view that the seat prices are too bunched (I have some sympathy with that view) or you could work on the basis that the variations from the norm will cancel each other out.

 

If you take the latter view, you might back 21-30 Lib Dem seats at 5/4 and 31-40 seats at 5/2, both bets with Bet365.  By placing appropriate stakes, you can get effective odds of slightly better than 1/3 that the Lib Dems will get between 21 and 40 seats.  Given the very local appeal of each Lib Dem candidate, it seems unlikely to me in practice that the Lib Dems will get fewer than 21 seats because their chances in different seats are much more loosely correlated than, for example, the major parties. 

 

Similarly, you can back the Conservatives to get 251-275 seats at 7/2 with Ladbrokes and 276-300 seats at 13/8 with William Hill, giving effective odds of slightly worse than 4/6 that the Conservatives will get between 251 and 300 seats - place the bet with William Hill first because it's more likely to be limited.  Conservative chances are much more correlated than the Lib Dem's chances, but this still looks like a good combination bet to me.  I've put some money on both of these combinations.

 

The same combination is available for Labour (251-275 seats at 7/4 with William Hill and 276-300 seats at 2/1 with Ladbrokes) for effective odds of slightly worse than 4/9.  The reward doesn't look quite good enough for me, but it's not far off either.

 

For a quirky bet, Coral offer a UKIP vs Plaid Cymru match-up.  The 7/2 on the tie looks like fair value, given that both are favourites in three seats.  I'm on.

 

The range of possibilities: how the constituency markets look in aggregate in March

In late November I had a look at how the constituency markets were assessing the parties' chances in aggregate - not just by looking at how the favourites stacked up in aggregate but also at how many seats in aggregate were in practice in play:

 

http://newstonoone.blogspot.co.uk/2014/11/conventional-wisdom-on-next-election.html

 

I thought it was about time, on the eve of the campaign, to look at this again.  Here are the aggregates of the best prices favourites on the seat markets:

Conservatives 275
Labour 278
Lib Dems 31
SNP 40
UKIP 3
Plaid Cymru 3
Greens 1
Respect 1
DUP 9
SDLP 3
Sinn Fein 5
Lady Sylvia Hermon 1

We now have Northern Irish seats, so we have a full house.  I have treated the Speaker's seat as being in the Conservative column, though different "most seats" markets treat his seat differently, so check this.

 

Since the end of November, the SNP have risen dramatically in the best-guess seat tally.  Correspondingly, Labour have dropped substantially.   Interestingly, the polls haven't actually changed much since December.  Sentiment has changed.  It seems to be a dawning realisation that the Scottish polls reflect an underlying reality.

 

Otherwise, the aggregate of the favourites has stayed very stable.  That is also interesting, because the constituency markets assume a level of recovery by the Conservatives and the Lib Dems which doesn't so far seem to be happening.

 

As you can see, both main parties are thought to be quite a long way from an overall majority. 

Just as importantly, Labour are thought to be slightly ahead of the Conservatives in the battle for most seats.  Even if you take the view, as I do, that the seat markets still underestimate the SNP's chances in Scotland, the two main parties are neck and neck.  You'd never guess that from the "Most Seats" market, where Labour can be backed on Betfair as of this morning at 2/1.  This price is crazy and backing Labour heavily on the Most Seats market should be an essential part of any portfolio of political bets.
 

How stable is that projected outcome?

As before, I've looked at how strongly fancied the favourite is.  And as before, I've worked on the basis that if there is a second favourite at or below 2/1, this is a true marginal.  I've presented the results in a tabular format, with the parties' range shown below:

https://docs.google.com/document/d/1o_021oOlU0YpvApb62zBI0MGVNXdaH3G3YppG8JYFMM/edit?usp=sharing
 

And again we see a substantial change from late November in both the Labour and the SNP columns.  The Conservative band has edged up slightly, but the Labour band has shifted down roughly 20 seats.  Meanwhile, the SNP band has moved forward by roughly 15 seats.

The consequence is that even at the outer edges of this measure of the parties' safe seats and marginals, neither party will get to an overall majority.  Neither party looks very likely to get to 300 seats - everything within this bound of probability would have to come right for the Conservatives for that to happen for them and most things within this bound of probability would have to come right for Labour for that to happen for them.

For those that are interested, here are the Northern Irish seats presented on this basis:

	DUP	SDLP	Sinn Fein	UUP	Independent
DUP	8	1	0	1	0
SDLP	1	2	0	0	0
Sinn Fein	0	0	4	1	0
Independent	0	0	0	0	1
UUP	1	0	1	0	0
Total	8-10	2-3	4-5	0-2	1

These will not affect the outcome of the main battle, of course.

Taking a broader view of what makes a marginal

Let's push the boundaries further.

As previously, I've also had a look at the position if we use the test of marginality as a seat having a second favourite that is priced at 5/1 or less. This table is complicated by the presence of 13 three way marginals (hence the extra row).

 
https://docs.google.com/document/d/1GVCbP7pn701XM-uOhJH7HL3QMYBFpDjr5RDP2BNTaMQ/edit?usp=sharing

(The independent is Claire Wright in East Devon, who is a localist environmental type, who has apparently been quite fancied at the bookies.)

The ranges of outcomes are now much wider than when I used a 2/1 cut-off for assessing marginals, but these wider ranges barely differ from late November.  The betting public aren't that sure of the SNP's chances. 

This stability of range is itself noteworthy.  These markets aren't shifting very much.  I haven't changed my views on the question of how correlated the results in different constituencies will be.  In my opinion, the answer is different for different parties.  The SNP will see very correlated results, since the election in Scotland is either going to be all about their turf (as seems likely right now) or Labour will have reframed it to some extent on UK-wide terms.  At the other extreme, Labour and the Conservatives are fighting multiple different battles and so the correlation will be much less.  To get a fuller version of my views on this subject, I went into this in much more detail last time, so have a look at the link at the top of the page if you want.

Again, for those that are interested, here are the Northern Irish seats presented on this basis:

https://docs.google.com/document/d/1EVhvEvf3wZDQmJbF55wNavDpAHUMRn0n6Jf5GGyPSwA/edit?usp=sharing

It is a more stable position than the rest of the UK, even at this level of marginality.

Conclusions



If the seat markets are to be believed, there is only a slim chance of either main party achieving an overall majority.  Even on the most generous interpretation of what makes a marginal, each main party is going to have to get close to taking everything thought to be in play to get there. 

Incidentally, it would be nice to be able to produce a neat graph which shows the exact implied probabilities of a hung Parliament, but the degree to which the results in individual constituencies will be correlated is uncertain, so it will be a matter of guesswork rather than science.

Are the seat markets to be believed?  Good question.  Two considerations push me in opposite directions. 

On the one hand, the two main parties have been regularly polling in the low 30s in the national polls.  On those national vote shares the winners in many seats will do so on relatively low local vote shares, meaning that the winners may be considerably less predictable at an individual level than the constituency markets suggest.  (The corollary to that is that some of the odds against shots may well offer good value.)  Set against that, the unpredictability is quite likely to cancel out to a considerable extent at an aggregate level.

So on balance I probably do believe the overall story of the seat markets.  That leads me to three conclusions:

1) Don't bet against a hung Parliament unless you get long odds.
2) Labour most seats is a terrific value bet at 2/1.
3) Since the Conservatives look unlikely to get above 300 seats (I'd guess at least 3/1), the next Government is very likely to be a Labour-led government.  Lay David Cameron as Prime Minister after the next election at anything close to, or even not very close to, current prices.  He's odds on at present to keep his job.  This is a crazy price.  Enjoy.

 

 

 

 

 

 

 

 

Conventional wisdom on the next election result

This post is effectively a follow-up to a short passage in one of my previous posts.  In my summary of the various individual party seat markets, I compiled a tally of the par seat outcomes.  I then asked myself how stable that projected outcome was.  On reflection, I felt the answer I gave didn't have very much precision about it and I wondered whether I could do better.  So here goes.

Where are we now?

Once again I've looked at the constituency markets and totted up the favourites in all 632 mainland GB seats to derive the current par outcome.  I used the markets as they stood on Tuesday 25 November, so these are already a little out of date, but the nice thing about this exercise is that it doesn't really matter very much if one or two seats are different or if I've made the odd mistake here or there.  Here's the current state of play:

Conservatives: 273 1/2

Labour: 301

Lib Dems: 31

SNP: 16 1/2

UKIP: 5

Plaid Cymru: 3

Greens: 1

Speaker: 1

(I've attached links to the full tables underpinning this and the other tables in this post at the end of the post for the super keen, but they aren't really very interesting.)

As you can see, not too much has changed in the last couple of weeks.  Labour are some way short of an overall majority, but some way ahead of the Conservatives.

And how stable is that projected outcome?

This is where I've done a bit of further thinking.  Because bookies price in terms of odds, we can derive implied probabilities on the chances of an upset.  There are a number of different ways in which you can do this - looking at how short the favourite is priced is one way.  The method I have chosen is slightly different, but I hope more informative about the chances of all the parties in a seat, not just the favourite.

So I started thinking about confidence levels.  How sure are these seats of being taken by the favourite?  So I retested them, this time marking seats as sure things if the second favourite was priced at longer odds than 2/1.  If a bet is priced at 2/1, that means that the bookie is presenting this as a 33% chance.  But allowing for the bookie's profit margin, this overstates the probabilities in reality [EDITED TO CORRECT OVERSTATEMENT].  So if a seat has no second favourite at or below 2/1, we can treat the favourite as having a pretty fair chance of winning.

If there is a second favourite at or below 2/1, this is a true marginal.  I've presented the results in a tabular format, with the parties' range shown below:

	Conservatives	Labour	Lib Dems	SNP	UKIP	Plaid Cymru	Greens
Conservatives	238	48	13	0	5	0	0
Labour	48	257	5	24	2	1	1
Lib Dems	13	5	18	3	0	1	0
SNP	0	24	3	9	0	0	0
UKIP	5	2	0	0	3	0	0
Plaid Cymru	0	1	1	0	0	2	0
Greens	0	1	0	0	0	0	0
THREE WAY MARGINALS	1	1	1	0	0	0	0
TOTAL IN PLAY	238 to 305	257 to 339	18 to 41	9 to 36	3 to 10	2 to 4	0 to 1

I hope this table is reasonably comprehensible, but in case it isn't, here's how it works.  Each seat has been classified as a safe seat (in which case I have tallied it in the box on that table where the party faces itself - so there are 238 safe Conservative seats, 257 safe Labour seats and so on) or a marginal.  If, for example, the seat is marginal between Labour and the SNP, I have recorded it in both places where those parties meet on the table.  So there are 24 Labour/SNP marginals.  I have treated the Speaker's seat as a safe Conservative seat.

This table wouldn't work quite so well if there were lots of three way marginals, but fortunately there is precisely one seat where three parties are priced at 2/1 or less: Watford.

In the final line, I've put the range of seat outcomes that might be expected for each party, bearing in mind what the constituency markets expect to be seats that are in play in this range.

This table is much more informative than I had expected.  It shows that within this range, the Conservatives are nowhere close to an overall majority.  Labour might creep over the wire, but only if everything goes right for them.

That leads onto the next question: how correlated are the results in the different constituencies?  I suggest that the answer is different for different parties. 

Leaving aside the Greens, the simplest parties to consider are the SNP and Plaid Cymru.  Both will be fighting on their own patch and on their own terms.  Whether or not they succeed will depend on whether their public regard their own prospectuses as compelling or whether they are minded to vote for other reasons.  For the SNP, seat tallies near either 9 or 36 are serious possibilities, depending on the answer to this question.  I see these party's results as highly correlated between constituencies.

I see UKIP's prospects as correlated, but not as much as the SNP's.  Their poll shares do not seem related to local candidates but on the alienation of a substantial chunk of the public.  However, they do appeal differently to previous Labour voters and previous Conservative voters, and it is easy to envisage Labour and the Conservatives having differential success in resisting their appeal.  Most of the seats in this prospect list are currently Conservative held, so there will be substantial correlation.  But for all the enthusiasm of UKIP supporters and a wave of money backing them, the seat tally is not expected to reach double figures on the current market prices.

The Lib Dems' chances are correlated more loosely still.  They campaign as local candidates, and this shows up in Lord Ashcroft's two stage polling in constituencies, where prompting for constituency matters gives the Lib Dems a big boost in seats where they have strong incumbents.  The correlation becomes stronger at the bottom end of the range.  They will start losing a lot of seats if the incumbency sandcastle cannot keep out the waves of national swing.  Incidentally, it is worth noting that the differential performance against Labour and the Conservatives is already largely priced in: Lib Dem held seats like Redcar, Norwich South and Burnley are already in the safe Labour column for 2015.

At the other extreme, we have Labour and the Conservatives.  The Conservatives are fighting on three fronts: UKIP, the Lib Dems and Labour.  These are three very different battles.  It is hard to imagine the Conservatives doing uniformly well against all three, though less hard to imagine them doing uniformly badly.

Similarly, how Labour perform against the SNP has almost nothing to do with how it will perform against the Conservatives or UKIP.  It is conceivable that Labour might sweep the board against both the Conservatives and UKIP even as it flounders against the SNP.  For Labour to get over 326, it would need more or less everything to go right in both of these essentially uncorrelated battles.  That's not a 2/1 shot, that's something closer to a 5/1 shot or longer (and that's accepting the 2/1 bar at face value).

Can you test this stability further?

Indeed I can.  I've also had a look at the position if we use the test of marginality as a seat having a second favourite that is priced at 5/1 or less.  That implies that the second favourite is a 1 in 6 shot, which again is likely to be on the high side, allowing for the bookie's profit margin [EDITED TO CORRECT OVERSTATEMENT].

Here's the equivalent table using that looser test:

	Conservatives	Labour	Lib Dems	SNP	UKIP	Plaid Cymru	Greens	Respect	NHA
Conservatives	197	94	31	0	11	0	0	0	1
Labour	94	205	10	42	5	3	2	1	0
Lib Dems	31	10	2	5	0	1	0	0	0
SNP	0	42	5	6	0	0	0	0	0
UKIP	11	5	0	0	0	0	0	0	0
Plaid Cymru	0	3	1	0	0	1	0	0	0
Greens	0	2	0	0	0	0	0	0	0
Respect	0	1	0	0	0	0	0	0	0
NHA	1	0	0	0	0	0	0	0	0
THREE WAY MARGINALS	13	10	8	4	10	0	0	0	0
TOTAL IN PLAY	197 to 347	205 to 382	2 to 57	6 to 57	0 to 26	1 to 5	0 to 2	0 to 1	0 to 1

This table gets more complicated for two reasons.  First, there are more parties in the mix.  And secondly, there are far more three way marginals: fifteen, in fact.  But I think it is still useful.

As you can see, the range of outcomes has got much wider.  At this level of testing for marginality, the SNP could worry about taking only the 6 seats they already hold - or dream of taking every seat in Scotland.  Either the Conservatives or Labour could have a healthy overall majority or a crushing defeat.

Things look a lot less stable at this level of confidence.  It seems that conventional wisdom is not so certain after all.

Perhaps.  But I come back to the point I made earlier on about correlated contingencies.  For example, it's a hell of a lot more likely that the SNP will tally 57 (or 6) seats than that Labour will tally 382.  The graph of possible Labour seat tallies would look curiously lumpy, with different correlated contingencies interplaying with each other in a largely uncorrelated way.  Either a Conservative or a Labour overall majority look to be firmly outside chances.  Equally, both major parties look most unlikely to suffer a Götterdämmerung.

Some betting observations

If you buy into the conventional wisdom on the seat markets, backing a hung Parliament is a complete no-brainer at any price north of 1/3 and probably shorter.  If the conventional wisdom of the seat markets is right, only Labour look in with any kind of a reasonable shout at an overall majority if the conventional wisdom is correct, and for the reasons I've given above, the odds on that should be long.  Dreams of a Conservative overall majority look to be just that: dreams.

Generally, I think the middle table is the best to work off.  It shows the range of reasonably expected outcomes.  The looser definition of marginals is, however, useful for understanding where the outer risks are.

I've always been keen on betting on a hung Parliament.  I'm now getting very keen indeed.  I've topped up again at 8/15 with Ladbrokes.

If you back any outcome other than a hung Parliament, you should be looking for long odds.  After all, you're going against the conventional wisdom of the seats markets.  You might want to consider the 326-350 seat bands for Labour or the Conservatives, since the odds of either going past 350 look very distant indeed right now.  These are not bets that I'm going to place though.

That's not to say that you wouldn't right to ignore conventional wisdom.  My view is that the markets are underestimating the volatility of seats on low poll shares for the major parties.  As it happens, my view is also that volatility in individual seats will probably cancel itself out in large parts, but you could reasonably take a different view. 

However, volatility for the SNP or UKIP will probably not be self-cancelling: both of these parties might either soar like rockets or fall like sticks.  Because the fortunes of the SNP and UKIP are pretty much completely uncorrelated, we could see both do the same thing at the same election.  At present, the SNP look more likely to sweep the board than UKIP, but I don't completely rule out the idea of a UKIP horde descending on Westminster.

There are a few more easy bets to make.  The SNP are currently 8/15 to win most seats in Scotland with Ladbrokes (or 5/6 over/under 25.5 seats).  You can instead buy the SNP at 21 on Sporting Index.  Using the 9 to 36 span shown by the middle table, you risk losing 12 or gaining 15 with a par point in the middle of 22.5 seats so it is effectively an odds against bet instead of an odds-on bet.  Yes, the best guess of conventional wisdom on the constituency markets is currently 16.5, but the seat markets are scrambling to catch up with the new reality of post-referendum polling.  On this one I prefer to trust the general markets right now (in particular, the prices in Glasgow and the surrounding area still don't reflect the likely impact of the Yes vote in that city on the SNP's chances).  If you can't stand it, pair the SNP buy of 21 with a bet on Labour most Scottish seats at 11/8.  One of these bets must win and both might.  Personally, I'm just buying the SNP.

UKIP next.  I pause, because I've been a persistent UKIP bear, only to be caught out by the markets repeatedly this year.  But the 1/3 that UKIP will tally under 19.5 seats with Ladbrokes looks very sound.  Even on the wider test of marginality, their upper limit looks to be 26.  I'm on.  Selling UKIP on Sporting Index at 9.5 is a good bet too - but be aware that if UKIP do soar like rockets, this bet might look very sickly - and expensive.  This is not impossible, and is inherently more likely than, for example, the Conservatives exceeding the top end of their range, because of the points I have made about correlated contingencies.

I intend coming back to these tables repeatedly in my betting.  I shall be worrying when I depart too radically from them. 

Footnotes for the super keen

Here are the detailed tables underpinning the summaries set out above.  In truth, they're not very illuminating, but I feel I ought to at least make my workings available.

https://drive.google.com/file/d/0Bygi8eZw-4q1TWEyeHZES19DMXMwSDFBZVRILUhmOUdWbG9V/view?usp=sharing

https://drive.google.com/file/d/0Bygi8eZw-4q1OE1YY1NTQk5IbEt2NExJd2ExQlJxTW5RakZN/view?usp=sharing

https://drive.google.com/file/d/0Bygi8eZw-4q1TW9ReTlsWEZPR2VsV1VUR0pFdXpPV2xNeXlF/view?usp=sharing