Historical polls

Projection of Tory victory narrows to 13-16pts as Corbyn’s ratings improve

Posted in Historical polls, Politics on May 18th, 2017 by Leo – Be the first to comment

I recently published analysis that showed leadership ratings are an excellent predictor of election results and used Ipsos MORI’s April poll to project a Tory win of 15-18pts. Their May poll has now been published and, with Corbyn’s ratings having improved and May’s remaining unchanged, that projection has narrowed to 13-16pts.

My analysis is based on a relationship that Matt Singh spotted in his celebrated 2015 pre-election article. As with my last article, this post doesn’t go into as much depth as Matt did – if he repeats the analysis he did last time, as he’s suggested he will, his projection will be more thorough than mine.

Nevertheless, the comparative leadership ratings in MORI’s last polls have a very strong relationship with the final gap between the parties at the election, so this is a useful guide.

With the new data, I’m looking – as before – at both the difference in satisfaction with May and Corbyn, and the difference in net satisfaction, ie also taking into account those who are dissatisfied.

Graphs are below, but the headline is: on the gap in satisfaction the Tories are projected to win by 13pts, and on the gap in net satisfaction they’re projected to win by 15pts.

With a linear regression (rather than polynomial) this increases to 14pts and 16pts, so the range is 13-16pts (this is Great Britain only, though that doesn’t make much difference to the gap).

This means the Tories are on course for a win that’s about as large as the one in 1983 – less than it seemed a few weeks ago, but still historically large.

It seems surprising that the projected gap has narrowed by two points when the correlation was very good both for the previous analysis and for this one. I initially thought it might be that views of Corbyn were relatively unsettled compared to past elections as he’d been leader for a fairly short time when the election was called – so the swing towards him might have been unusually large. But actually the change in his satisfaction over this period is only around median – he’s gained less in terms of relative satisfaction, since the last poll, than the swing towards Howard in 2005, Blair in 1997 and Kinnock in 1992. The answer may just be that the ‘model’ is quite sensitive and is moved by a change of a few points in satisfaction, but still leaves an overlap around 15-16pts.

So, regardless of the reason – and despite Corbyn’s slightly improved satisfaction score – the projection still points to the largest win by any party for at least 34 years.

Leadership satisfaction polls suggest the Tories will win by 15-18pts

Posted in Historical polls, Politics on May 9th, 2017 by Leo – Be the first to comment

Quite long and data-y. Key points:

  • Historical polls show the gap between satisfaction with Labour and Tory leaders, in polls close to elections, is an extremely good predictor of the gap between the parties at the election.
  • It is actually a better predictor of the gap between the parties than voting intention data.
  • The measure suggests the Tories are on course for a 15-18pt win.
  • This means current polls may be overstating the Tories’ lead.

Two years ago this week, Matt Singh correctly argued, against the consensus, that the Tories were on course for a clear win.

This post recreates one of the analyses Matt used to come to his conclusion. Using it, I suggest the Tories are on course for a 15-18pt victory.

I’m using Mori’s long-running data on satisfaction with the party leaders. This was one of several that Matt used and is being widely talked about as an apparent sign that the Tories will win (note, Matt used several other measures as well – my analysis is less thorough than his and I’m not suggesting this is such a serious study as his was).

Some high-profile commentators treat this satisfaction data as if it’s a direct substitute for voting intent. So when, for example, 23% say they are satisfied with the job Corbyn was doing, some people have interpreted that as meaning Labour would get 23% of the vote. That is not borne out by the data.

The following charts compare satisfaction with the leaders, from Mori’s polls taken six weeks before the election (chosen so we can compare with the latest Mori poll, from April 2017).

The first shows the percentage satisfied with the Prime Minister minus the percentage satisfied with the Leader of the Opposition, compared with the governing party’s lead at the election.

The second is essentially the same, but shows the difference in net satisfaction between the leaders, so also takes into account how many are dissatisfied.

For each I’ve used a polynomial regression, as Matt did. This points towards a Tory victory of 15pts if we compare only those who are satisfied. If we compare net satisfaction the Tory victory is 17pts. Both have nearly equally good r-squared values.  The fit is almost exactly as good with a linear regression but in that case the Tory victory is around 1pt greater. So I suggest this points to a Tory victory of 15-18 points.

(This is in GB only, but that shouldn’t make much difference to the gap between the parties expressed in terms of UK results.)

This suggests the Tories are likely to exceed their 1983 victory, but probably not 1931.

It would mean current polls are mostly overstating the Tories’ lead. The last five have given the Tories a lead of 16-22pts, which appears a little high.

That said, it may be that opinion has shifted since the latest Mori poll. Perhaps the unusually short period between elections means opinion is less settled than it normally is before an election, so the 6-week-out poll isn’t as accurate as it normally is. The next Mori poll, out in a couple of weeks, will tell us whether satisfaction with the leaders is indeed still shifting.

On a final note: I was wrong. I’ve said a few times that I think the suggestion that analysts should look beyond voting intention numbers, to underlying figures, was like astrology – you could always find something in the underlying numbers to, retrospectively, fit with what actually happened.

But this analysis has changed my mind (perhaps it should have been changed by Matt’s analysis two years ago). I’ve also run the same dependent variable – election results – against the voting intention data in the same Mori polls that I took the leadership-satisfaction scores from. Unexpectedly, to me at least, the correlation between voting intent (in terms of gap between the parties) and the election result was worse than the correlation between leadership satisfaction and the result (the same is still true of the final Mori poll before the election, although the difference is smaller):

In short, if you want to project the gap between the parties at the election, it’s better to look at the leadership satisfaction – and apply the regression formula – than it is to look at voting intent.

Unless perceptions of Corbyn and May shift dramatically, the Tories are heading for the biggest win since before the Second World War.

How low can Labour’s support go? What past elections & European politics suggest – Polling Matters

Posted in Historical polls, Politics, Polling Matters on October 27th, 2016 by Leo – Comments Off on How low can Labour’s support go? What past elections & European politics suggest – Polling Matters

On Polling Matters this week I talked about what might happen to Labour’s support over the rest of the Parliament.

Regular readers of this site might remember that I’ve previously compared how oppositions have stood in the polls 18 months after elections with how they then did at the subsequent election (using Mark Pack’s brilliant collection of historical polling data).

For this week’s episode I updated this analysis with the 2015 election (which was an outlier, as Labour underperformed how they’d be expected to do – largely because of the polling miss). The analysis suggests that, between this point in a parliament and the subsequent election, polling leads typically roughly halve.

This happens regardless of whether it’s the government or the opposition that’s leading in the polls at this point.

I found this surprising and it seemed like it can’t be right. I had thought that this was typically a low point for governments, and that they usually recover support by the time an election comes. But the evidence doesn’t really seem to bear that out – and it appears the opposition did gain ground ahead of the 2001 and 2005 elections.

Obviously this is a crude model. It doesn’t take into account many things. But for what it’s worth it suggests that Labour – currently about 12pts down – is on course for a 6pt election defeat, which is less than I’d expected.

Historical-polls

 

But here’s another view on the question of Labour’s polling floor.

If we look at other centre-left European parties that, like Labour, were scoring between 35-45% in the late ’90s and early ’00s, we don’t see much evidence that Labour is currently at the lowest point it can get. All of those parties have scored lower than Labour in national parliamentary elections. Most of the others have gone below 25%.

Clearly different electoral systems – and national politics – are an enormous factor. What happens in one country isn’t inevitably replicated in another. But this alone suggests that Labour has no assurance it can call on the support of 30% of the public at a general election. Other major centre-left parties have found that the ground can indeed fall away beneath them.

centre-left

I talked about this, along with Ukip and Theresa May’s in-tray, with Keiran and Asa Bennett of the Telegraph.

Audio:

 

Video:

 

A year of Corbyn: how the Labour leader compares with his predecessors

Posted in Historical polls, Labour leadership, Politics on September 11th, 2016 by Leo – 1 Comment

The day Corbyn took over as Labour leader I posted a chart of how his predecessors had done in their first 12 months, so we could compare polling of Labour during Corbyn’s first year. Every three months I’ve checked in on progress (here, here and here).

Corbyn has been in charge of the party for a year and here is the last update in the series (methodological note below).

It shows that Labour is not the most unpopular it’s ever been at the end of a leader’s first year. Fewer people said they’d vote Labour in 2008 than say the same now. Labour has no less support now than it did after Michael Foot’s first year.

You could argue either way about how badly the precedent suggests Corbyn’s doing. On the one hand, every other Labour leader who took over in opposition when it was polling below 40% (Kinnock, Smith, Miliband), finished their first year with it above 40%. Corbyn finishes his first year at around 30%.

On the other hand, Callaghan, Foot and Brown all lost much more support in their first year than Corbyn did. So it’s hard to argue, using just this data, that he’s the most unsuccessful post-war leader.

The comparison also suggests that the leadership challenge (which came between the 9- and 12-month points in this chart) has had little effect on voting intention. Polling of Corbyn’s Labour has followed a common historical pattern: gaining support in its first six months, then losing it in the second six (as did Gaitskell, Wilson, Kinnock, Smith and Blair).

First 12 months

Given where Labour is now, how can it expect to do at the next election?

A rule that has never been broken is that Labour oppositions always lose support between the end of their leader’s first year, and the general election.

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Seven months to go, historical polls still point to a narrow Tory election lead, with Labour the largest party

Posted in Historical polls, Politics on October 1st, 2014 by Leo – 1 Comment

Seven months until the General Election it’s time for an update of my chart of what historical polls and votes can tell us about the election ahead.

The earlier posts are available here, including discussions of the methodology. As ever, I’m using Mark Pack’s brilliant spreadsheet of historical polls.

The new analysis suggests that:

Opposition lead at the election =

(0.6 x Opposition lead seven months before the election) – 4.3pts

According to UK Polling Report, Labour’s current lead is 4pts. This means the analysis suggests a Tory lead after the election of just under 2pts: probably not enough for a majority, and with Labour the largest party.

This is almost exactly the same prediction as from polls a year before elections. It is also similar to – though marginally better for the Tories than – the prediction from polls two years before elections.

But now focus on the elections in the area in the red box below: where the polls were narrow at this stage. In these cases there is a huge amount of variation in the results: from a healthy Opposition victory (’79) to a comfortable Government majority (’87).

So from where we are now, previous elections suggest either main party could build a majority-sized lead.

That said, the fact the polls have followed the historical trend for at least the last 17 months provides some evidence to support the model’s prediction of a very small Tory lead.

Health warnings

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12 months to go, historical polls suggest a knife-edge election result

Posted in Historical polls, Politics on April 9th, 2014 by Leo – 7 Comments

In two previous posts, I looked at how we can use past polls and elections to shed light on what current polls tell us about the next election. Today, I’m publishing an update, on how to interpret polls one year before the election: less than a month from now.

The interesting bit

According to the historical trend, election results relate to polls 12 months before as:

Opposition lead at the election =

(0.5 x Opposition lead a year before the election) – 3.5pts

That is, on average, polling leads halve (whichever party is leading) and move 3.5pts in favour of the government in the 12 months before an election (the real-world logic of requiring these two steps isn’t obvious and there’s no suggestion they actually happen in this order – but it’s what the regression produces).

This means, a Labour lead of 6-8pts 12 months out would point towards a tie in vote share at the election – making Labour the largest party and probably just short of a majority:

'79 and '87 had seriously odd 12 months before the elections

This would suggest Labour’s current poll lead – 4pts – points towards a narrow Tory win on vote share at the election, of around 1.5pts. Again, this would probably put Labour as the largest party.

Should you pay any attention to this graph?

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What do old polls show about the next election?

Posted in Historical polls, Politics on January 12th, 2013 by Leo – 1 Comment

I wrote a post last year about old opinion polls and how well they predict future elections. It compared election results with polls taken 18 months after the previous election, and also compared polls taken two years before an election to the result of that election.

It’s now coming up to two years before the next election and the second part of my post has got a bit of attention.

John Rentoul in the Independent on Sunday argued that this kind of analysis is all well and good but we shouldn’t pay too much attention to where the polls are at the moment – there are too many unpredictable events that will change things over the next two years, and what matters is how the parties respond to them.

On Labour Uncut, Rob Marchant focused on the implications of the “two years before the next election” chart (below) and concluded that Labour is on the border between being on course to win in 2015 or not.

The “two years out” data do suggest, as Marchant says, that Labour’s current 11pt lead is about on the cusp of where an opposition needs to be if it’s to have most votes at the election. Only once – ’64 – has an opposition won when it’s been ahead by less than 10pts at this time.

But Rentoul is right that current polls can only take us so far: indeed the regression showed a 40% correlation, not a perfect prediction.  Events, and the parties’ reactions to them – politics – will do most of the shaping of what happens, and whether Labour’s lead goes up or down.

This is probably about as far as we can get looking just at overall national voting intent and past elections. But we can learn more by digging a bit deeper into where Labour’s lead came from.

About 15% of Labour’s current support is from people who voted Lib Dem in 2010*. It was their move to Labour in late 2010 that gave Labour a polling lead which it has kept pretty much consistently (except a brief period in early 2012). The fact these voters have largely stayed with Labour for two years suggests their support is fairly stable. But who knows what they will do when the Lib Dems start stepping up an election campaign, or if Clegg is dropped and the Lib Dems start trying to present a clean slate.

And it’s important to think about how this Lib Dem defection will work at the constituency level. Several people have written about this, but for me this piece by Mark Gettleson nails it. There are 33 seats where the Tory majority over Labour is less than the proportion of the vote that moved from Labour to the Lib Dems between ’97 and ’10. If these move back (though in 18 years there’s a lot of churn in a constituency), Labour would gain those seats directly from the Tories. (There are of course also seats, balancing this, that the Tories will be trying to take off the Lib Dems – 20 of their 40 targets)

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Past elections suggest Labour’s prospects are better than most commentators think

Posted in Historical polls, Politics on January 9th, 2012 by Leo – 7 Comments

Commentary on the difficulties facing the Labour Party – leading in nearly every poll for over a year – sometimes puts me in mind of Bill Shankly, the Liverpool manager of the ‘60s and early ‘70s. Responding to a journalist’s question about a supposed crisis at the club, the great man said, “Ay, here we are with problems at the top of the league”.

Likewise, despite Labour’s consistent polling lead, the impression from the comment pieces, blogs and tweets is of a party struggling to find supporters. The logic is that, firstly, Labour’s lead is smaller than might be expected against a government undertaking such spending cuts, and, secondly, that the government is likely to recover and overhaul that lead between now and the next election.

The first of those points may be subjective, but the second can be tested against what’s happened in the past. Mark Pack has compiled the voting intent results from all opinion polls published since 1945, which allows us to do just that.

November 2011 marked 18 months since the last general election. At that point, Labour were on average 4.6pts ahead of the Tories, a score that has since slightly reduced due to Cameron’s veto bounce.

Comparing this score with opposition parties’ poll scores relative to governments’ 18 months after past general elections allows us to benchmark how Labour are currently doing. It also allows us to estimate Labour’s result in the next general election.

A regression analysis of historical polls 18 months after an election, relative to scores in the next general election can provide a model to analyse where we are now (see below for the detailed methodology). The analysis suggests that performance at this point is in fact a pretty good prediction of performance at the next election: it predicts nearly 60% of the result of the next election, with a very high level of confidence (p=0.002).

If a party is leading at this point, it tends to be leading at the election. However, the gap between the government and the main opposition partly typically halves over the remainder of the parliament.

Therefore, given the current position, the historical data suggest Labour should expect to win the next election by a small margin, of a little over two percent.

However, these polls weren’t conducted equally far before the forthcoming election. The Feb ’74 election, for example, was 44 months after the previous election, while the 2010 election was 60 months after the previous one.

So, as well as comparing election results with polls 18 months after the previous election, we can compare the results with polls exactly two years before that election date.

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