#Datablog: How the general election was won and lost in Croydon

By - Thursday 9th July, 2015

Robert Ward dives deep into the data of Election 2015 and, with a little help from calculated assumptions, paints a picture of how the borough made its mind up

Breakdown of the Croydon South result.
Image author’s own.

The recent general election reminds us that just because there’s a consensus doesn’t mean that the consensus is right. Most predictions were for a hung parliament. The polls fooled pretty much everybody, including me.

The polling organisations have set up an enquiry. I have taken a much more modest look at our three Croydon constituencies to see if that might give us some clues on what happened.

What we would like to know – what the election always hinged on, really – is how individual voters changed their allegiances since 2010. That’s a complex problem with limited information. So we have to simplify, hopefully without compromising our conclusions too badly. You will have to make your own assessment of how badly.

I assumed that all those who voted for ‘other’ parties in 2015 had voted for ‘other’ parties in 2010

Firstly, I assumed that everyone who voted for the Greens and UKIP in 2010 voted the same way in 2015. Independents and fringe party candidates are another complication. These parties generally polled much lower in Croydon in 2015 than they had in 2010 so I assumed that all those who voted for ‘other’ parties in 2015 had voted for ‘other’ parties in 2010.

My first more significant assumption is where the new Green voters came from. I assumed that Croydon Green voters came from the Tories, Labour and LibDems roughly in line with a national YouGov poll.

That same YouGov poll estimated how people had changed between 2010 and 2015. I used this as a starting point for the Croydon constituencies, varying it as little as possible to match the actual 2015 Croydon results.

UKIP votes came mainly from the Conservatives, but the proportion of 2010 Lib Dems who voted UKIP was also high

Croydon South, the results of which are shown above, was the easiest to analyse. There were no ‘other’ candidates at all in 2010 and those that stood in 2015 attracted a very small vote. Croydon North was only slightly more complicated.

In both these constituencies, I found that our Labour and Conservative voters were more loyal than the national average, Labour voters slightly more so than the Conservatives. Voters switching between Labour and the Conservatives, the determinant of many past elections, was rare.

In the new multi-party political climate, the big stories are the source of new UKIP voters and where the 2010 Lib Dem voters went to. I found the source of the UKIP vote was consistent across Croydon, coming mainly from the Conservatives, but the proportion of 2010 Lib Dems who voted UKIP was also high.

Tory Chris Philp’s performance in Croydon South saw good support from 2010 LibDem switchers partially counterbalanced by losses to UKIP

For the Lib Dems there were marked differences. In Croydon South, the 2010 Lib Dems went to the Conservatives by a two to one margin over Labour. In Croydon North, this group went strongly for Labour by more than six to one over the Conservatives.

Breakdown of the Croydon North result. Table author’s own.

So the performance of Labour’s Steve Reed in Croydon North is explained by his strong support from 2010 Lib Dems. Tory Chris Philp’s performance in Croydon South was the result of good support from 2010 LibDem switchers, partially counterbalanced by losses to UKIP (in line with the national trend).

Croydon Central was, of course, the battleground (or the boxing ring, if you picked up April’s edition of the Citizen). Here, the Conservative majority over Labour of around 3,000 was reduced to just 165. Croydon Central had a particular complication – the presence on the 2010 ballot paper of the former Tory MP who has since defected to Labour, and the BNP. Together these took around 10% of the vote in 2010. Neither stood in 2015.

Barwell ‘leaked’ fewer votes to UKIP than his fellow Conservative candidates, both locally and across the country

To help us we have a constituency poll by Lord Ashcroft conducted a week before the election. His prediction, controversial at the time, was actually rather accurate, although some of its assumptions led to it over-estimating the Tory majority.

Breakdown of the Croydon Central result. Table author’s own.

The voters questioned by Lord Ashcroft did seem to have forgotten the other candidates from 2010 even though some 10% of them had voted for them. I used this poll as a guide for the 2010 main party voters which enabled me to estimate how the 2010 ‘other’ voters had voted in 2015 – marginally more to Labour than the Tories, as with the 2010 Lib Dems.

The conclusion for Croydon Central is that Tory Gavin Barwell retained a slightly higher number of 2010 Tory voters than was achieved by Chris Philp or Vidhi Mohan, the Tory candidate in Croydon North. Barwell was also able to reduce the UKIP ‘leakage’ to below the rate seen in neighbouring constituencies, as well as nationally. This combination was (just) enough to counterbalance the Labour leaning trend for 2010 ‘other’ and Lib Dem voters.

If you live in Croydon Central, brace yourself for lots of canvasser attention again in 2020

The very different Lib Dem switching patterns across an area the size of Croydon and, although we did not see it in Croydon, the variable UKIP pattern across the country, mean national polls may have had their day. Some countries abandoned these some time ago in favour of constituency polls in marginals. The problem for the pollsters is that this is much more expensive.

For Croydon in 2020, national issues will dominate as they always do. Whether the Lib Dems survive, what a post-referendum UKIP might look like, and who might be leading the main parties will be crucial. Closer to home, Croydon Central will likely remain our marginal even after the boundary changes. If that’s where you live, brace yourself for lots of canvasser attention again in 2020, and probably more pollsters too. A lot of people are going to be very interested in whether you’ve changed your mind.

Robert Ward

Robert Ward

Engineer and project manager, started work on the railway but most of career in oil exploration and production. For the last fifteen years specialised in helping businesses improve their performance. Conservative Party candidate to represent Selsdon and Addington Village on Croydon Council. He tweets as @moguloilman.

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