In this post, the team at electionforecast.co.uk discuss their current predictions for London. They predict that the Labour Party will increase its share of the seats in the capital, largely at the expense of the Conservatives. Furthermore, it is highly probable that Labour will perform better in London on May 7th than in the rest of England.
See Tony Travers’ analysis of the campaign in London here.
As Tony Travers has argued, for many years the capital was a political microcosm of the UK as a whole: London vote shares for the three main parties mirrored their national vote shares in most general elections up to 1997. Since then, Labour has started to increase its presence in London constituencies. As the plots below indicate, in 2010 Labour won significantly more seats in London than the Conservatives – a performance they failed to replicate across the UK.
Our headline forecasts for the region suggest that Labour is likely to increase the number of London seats that it holds in 2015. The graph below shows our predictions for each constituency in the region. Our current prediction is that Labour will win 46 seats, the Conservatives 22, and the Liberal Democrats 5. This implies that Labour will win two seats from the Liberal Democrats (Brent Central and Hornsey and Wood Green), and 6 from the Conservatives (Brentford and Isleworth, Croydon Central, Ealing Central and Acton, Enfield North, Finchley and Golders Green, and Hendon).
What, then, is the probability that Labour will continue to outperform in London relative to other regions? We can use our model to simulate the forthcoming election many, many times, and for each simulation we can record the result in each constituency. There is considerable variation in the results we record (reflecting our uncertainty in specific election outcomes), but we can use the distribution of these simulated results to work out how probable each outcome is.
We can then use the simulated constituency results to compare Labour’s forecast performance inside the capital to its performance in constituencies outside of London. (As it is clear that Labour is very likely to lose a large number of seats in Scotland, we exclude both Scotland and Wales from the calculation here.) This allows us to calculate the difference between Labour’s London-only seat gain, and its England-wide seat gain. We plot the distribution of these differences below.
The x-axis measures, in a given simulated election, whether the “swing” to Labour (in terms of the proportion of seats) is larger or smaller in London than in the rest of England. When Labour performs better in London than in the rest of the country, they will gain proportionally more seats, and the variable measured on the x-axis will be positive. When Labour under-performs relative to the rest of England, this number will be negative.
The y-axis gives the percentage of simulated elections pertaining to each value. The higher the bar, the more likely is a particular result. The bars coloured in red imply that Labour outperforms in London relative to the rest of the England.
As the plot makes clear, there is a relatively high (almost 80%) probability that Labour will secure a greater “swing” in terms of seats inside the capital than outside. This corresponds to the historical pattern that shows that when voters swing toward Labour nationally, they do so even more in London.
Overall, London is likely to provide fertile ground for the Labour campaign in 2015. If the results are as close as expected, these seats – and any Labour gains – could be vitally important in any post-election government negotiations. We will continue to update our forecasts with new polling data as it is released, and updated forecasts for London, as well as for the rest of the UK, can be found at our website.
Note: Forecasts are accurate as of April 3rd, 2015.
Jack Blumenau is a PhD candidate in Government at the London School of Economics.
Chris Hanretty is a Reader in Politics at the University of East Anglia.
Benjamin Lauderdale is an Associate Professor in Methodology at the London School of Economics.
Nick Vivyan is a Lecturer in Quantitative Social Research at the Durham University.
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