Understanding the Local Elections Projected National Share (PNS) in 2023

by John Curtice and Stephen Fisher, 3rd May 2023.

Much of the speculation about what might happen in the English local elections this week has focused on how many seats each party could or should gain or lose. The Conservatives have seemingly accepted an analysis for the Local Government Chronicle that they could lose 1,000 seats – presumably in the hope that they will do better than that – while Labour have suggested they might win 400 – presumably anticipating they will gain rather more. We can expect many a judgement to be cast on Friday on the basis of this evidence. 

However, given that these elections are held under single or multi-member plurality, seats won and lost can be a poor guide to how well a party has done in the ballot box. A party whose vote has fallen less than that of their principal rivals may gain seats even though it has lost votes. A third party whose vote is geographically spread may make a substantial advance in votes yet reap little reward in terms of seats. Meanwhile, seats won and lost only provide an indication of whether a party has lost or gained ground as compared with when the seats up for grabs were last contested.

These caveats are particularly important this year. Ninety per cent of the seats were last fought in May 2019, when Theresa May was Prime Minister and Jeremy Corbyn Leader of the Opposition, both of whom were rebuffed by voters in the local ballot boxes. In contrast, the Liberal Democrats and the Greens performed relatively well four years ago. Meanwhile, just over 5,000 of the 8,000 seats at stake are in relatively small shire district councils, where in most instances all of the seats are up for grabs in wards that elect more than one councillor at the same time. The outcome in these districts will dominate the headline numbers. Moreover, in many instances they are places where Labour is not competitive locally, and the scale of any Conservative losses will depend not on how well Labour do but, rather, on the performance of the Liberal Democrats.

Yet we cannot assess the party’s votes by simply adding up the votes cast (even if we had the resource to collect them all on election night). In England (unlike Scotland and Wales) it is never the case that the whole country votes in local elections at the same time. The places that vote one year are politically different from those that vote in another. For example, unlike last year, there are no elections in Labour-dominated London.

Given all these limitations, a key indicator of party performance that has come to be part of the ritual of local election night (or the following day) is the calculation of a ‘projected national share’ (PNS). This is an estimate of the share of the vote that the principal parties would have won if, across Britain as a whole, voters had behaved in the same way as those who did vote in the wards that were contested by all three principal parties in this year’s English local elections. It provides a single, seemingly straightforward measure of party performance that can tell us not only how well or badly a party has done as compared with four years ago, but also as compared with local elections over the last forty years – even though the places in which local elections are held varies considerably from one year to the next.

Yet almost inevitably answering such a ‘what if’ question is not as straightforward as it might seem. Given the large number of wards being contested, the calculation of the PNS has to be made on the basis of a sub-sample of the local contests. None of the parties fight all of the wards being contested, and some may well fight fewer wards than others. At the same time, local election results in England tell us nothing about the performance of the nationalist parties in Scotland and in Wales. Any estimate of the PNS is affected by the decisions that are made about how best to address these issues.

Consequently, it is not surprising that there have sometimes been differences between the PNS we have calculated for the BBC at previous local elections and that calculated by the local election experts, Colin Rallings and Michael Thrasher of Plymouth University, whose National Equivalent Vote (NEV) appears each year in The Sunday Times. Those differences have typically been limited with neither the PNS or NEV consistently better or worse for any party. That said, since 2015 there has been a tendency for the PNS to be higher than the NEV series for the Liberal Democrats and Others, and correspondingly lower for the Conservatives and Labour. Some of the possible reasons were discussed in our blog post from last year

One of the key features of British electoral behaviour since the EU referendum has been a strong link between party support and whether people backed Leave or Remain. Leave voters – and Leave voting areas – are more Conservative, while Remain supporters – and areas – are relatively Labour. This pattern has also been reflected in local elections. Consequently, since the Brexit referendum it matters a lot whether the councils up for election are disproportionately in Leave voting areas or Remain supporting ones. 

This year the elections, which cover nearly 80% of provincial England (that is England outside London), occur in places that were more inclined to vote Leave. True, at 56%, the average 2016 Leave vote in places with local elections this year is only slightly higher than the 55% figure for those parts of provincial England that do not have local elections this year. However, it is still well above the 52% who voted Leave across Britain as a whole. After all, Leave only won 42% in London together with Scotland and Wales, in all of which there are no local elections this year.

Between 2017 and 2021 the swing to the Conservatives since previous local elections was higher in Leave voting areas than in Remain inclined areas. However, last year the swing since 2021 to Labour in provincial England was greater in Leave voting areas than in Remain supporting places, even though, at the same time, the swing to the Conservatives since years before 2021 was still higher in Leave inclined England. The Brexit divide in Conservative and Labour support was still strong, just a little weaker in the 2022 than in the 2021 local elections. This year we may find that the Brexit divide is still wider than in 2019, but less sharp than in 2021 or 2022. 

As we described in 2018 here, in 2019 here, in 2021 here, and 2022 here the regression and projection methodology we have developed in recent years (which rests on comparing the parties’ performances this year with multiple previous years) takes into account both (i) any different patterns of change since different baseline years in Leave and Remain areas, and (ii) the balance of Leave and Remain support in local authorities in places with local elections as compared with those without. 

Much political attention on Friday will be on the relative performance of the Conservatives and Labour. Last year, in the final weeks of Boris Johnson’s premiership, Labour had a five-point lead in the PNS. Since then, Labour’s lead in the opinion polls has widened during Liz Truss’ brief tenure as Prime Minister, but then narrowed somewhat under Rishi Sunak. Nonetheless, Labour are still further ahead in the polls now than at the time of last year’s local elections – and indeed than it has been at any round of local elections since 2010. A key question, therefore, is whether the parties’ performances in these local elections reflects that bigger Labour lead in the polls. Will Labour beat their previous best score since 2010, that is, the seven-point lead Labour enjoyed in 2012? And can Sir Keir Starmer open up a double-digit lead in the PNS as Sir Tony Blair and David Cameron did before their respective general election successes in 1997 and 2010? Those are the key questions we will be attempting on Friday.

John Curtice is Professor of Politics at the University of Strathclyde.

Stephen Fisher is Professor of Political Sociology at the University of Oxford.

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