Forecast update: Brexit probability increases sharply

Brexit probability has risen sharply, with the NCP Brexit probability index now at 33%. Thus the chances of Britain voting to Leave the EU are higher than at any time since last year’s general election result confirmed that the referendum would take place. What’s happened?

Well, before today the data flow was a string of online polls saying what online polls have been saying all along, together with limited evidence (one ICM phone poll over the long weekend) of relative movement in phone polls. At the time a bank holiday outlier seemed likelier than the phone online gap – that’s been present for years – suddenly vanishing altogether. But sometimes, less likely things happen, and so it may have proved here.

I say “may” because we haven’t heard recently from the other two experienced phone pollsters, Ipsos MORI (expected in the Evening Standard on Tuesday or Wednesday) and ComRes, who will have at least one more poll before next the 23rd of June. ORB’s phone poll still showed a 5 point Remain lead, compared to a 10 point Leave lead in its online poll, but I would put more weight on ICM.

So it looks as though the phone-online gap has been substantially reduced at the same time as both methods showing a swing towards Leave.

In other words, the facts have changed, so I’ve changed my mind. Some will say that the facts had already changed and this move is the model playing catchup. The problem with that view is that simply taking the last n polls (as many polls-of-polls do) and ignoring the persistent modal difference is that you tend to get an awful lot of artificial volatility.


Simple averages have moved around so much – in both directions – that whenever the real move eventually happened, the simple averages were almost bound to call it first. The problem is that they’d previously “called” several moves that never actually materialized.

The difference now is that we have ample evidence that the move is real, despite the uncertainty about its size, and since it’s coincided with the phone-online gap closing, that adds up to big increase in the chances of Brexit.


Moves of this size aren’t ideal in forecasts, but inevitible given the paucity of one mode of poll so late in the campaign. Further volatility is to be expected going forward – if ComRes and Ipsos MORI suggest that a significant phone-online gap remains, the outcome will be very different than if they too suggest it has disappeared.

The hardest time to measure public opinion is when it’s moving, and it has clearly moved. So it may take a couple of days to unpick the latest poll movements, but the pattern is clear, even if uncertainty remains around the level.

I said on TV a few months ago that for pollsters and forecasters, this referendum would be the biggest challenge of their careers. On that, my mind has not changed.

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  • Scott Reed

    Hi Matt… great article. This sentence leaves me a little confused: ORB’s phone poll still showed a 5 point Remain lead, compared to a 10 point Leave lead in its phone poll, but I would put more weight on ICM.

    Should it be “10 point Leave lead in its online poll”

    • Number Cruncher Politics


  • mrodent33

    Wow… you just have to look at that graph to see an ominous correlation between the undecideds making their minds up and the leave graph rising.

    Personally I’m praying the pound starts to sink between now and Thursday week… it may be the only thing which could bring stop the Brexisuicidal idiots.

    • Craig Grannell

      Given that tens of billions have already been pulled out of the UK and Sterling’s regular kicking in recent weeks, I don’t think anyone cares. This is about nebulous catchphrases more than reality. Anyone who’s not rich and voting Brexit is going to be in for a nasty shock when it happens and the ramifications become clear.

    • David n

      Honestly, that would be plain and simple market manipulation. Brexit would not result in some fundamental, overnight shift. The process would be slow and deliberate and done in a way that would avoid economic shock to companies. I can only conclude the recent market turmoil is either unrelated to Brexit or manipulation by hidden interests.

      • mrodent33

        “The process would be slow and deliberate”

        Hahahahaha. By 4pm on June 24 there would be £/€ parity. Investors and forex traders are not known for their slow and deliberate actions in the wake of a economic tidal wave!

  • Bob Lawbla

    Economic downturn is a small and temporary price to pay for regaining national sovereignty. From your closest ally America, we support your decision for a Brexit!!

    • mrodent33

      Motherhood and apple pie. Only trouble is we’d have LESS sovereignty after Brexit. Firefighting would start on June 24 and wouldn’t end until we had accepted a Norway-like deal: 95% of the rules and no seat at the top table.

      • Bob Lawbla

        “In the past 20 years, there have been 72 occasions when Britain has opposed a particular measure on the Council of the European Union. On all 72 occasions, we have been outvoted by the other member states. ”

        “Since 1973, the UK has lost 101 cases in the European Court and won only 30. That’s a failure rate of 77%.”

        How’s that seat at the table working out for you?

        • mrodent33

          Hahaha. Clueless. Most of the countries of Central/Eastern Europe share the UK’s ideological stance. But the central institutions were indeed set up to favour the France/Germany Statist model, rather sclerotic.
          I favour change from within rather than transforming to a vassal nation from without à la Norway. Brexit would result in precisely that: the markets would see to it.

          As you’re from Asylum America, why don’t you concentrate (rather hard) on your own problems (e.g, oo, let me think, firearms!). You don’t really understand much about the EU.

          • Bob Lawbla

            So your response to my accurate statistics of the UK being voted down by the EU body time and time again.. is to call me clueless and then tell me I am wrong without backing it up with any facts of your own.

            I mean.. I’ve watched UK parliament fights, but even they tend to back up their nonsense with some facts.

            You favor a change from within, which would be great if it was possible. The UK’s greatest leverage has always been it’s threat to leave the EU. However, if the UK votes to remain you will effectively lose any leverage you had before.

            Also, the trade deficit that the UK has with the EU is by and far a large enough bargaining chip for adequate trade deals.

          • A Request

            Could you provide your sources for the accurate statistics ? Preferably from the ECJ itself or a reputable/affiliate statisticians’ cabinet.

            It’s not that I doubt them, I want to put them in perspective with other rulings of th ECJ.

          • Bob Lawbla
  • wyliecoyoteuk

    Economic downturn hits the poorest hardest.
    Unemployment, rising debt, loss of property.
    Only the wealthy can ride it out without pain.