Will Nate Silver be wrong about Scotland, like he was wrong about Britain?

Silver has a reputation in America, but he hasn't earned it this side of the Atlantic.

Psephological wunderkind Nate Silver has been asked by the Scotsman to give his thoughts on the potential outcome of the referendum for Scottish independence. His thoughts are “no”:

Only a “major crisis” south of the Border could turn the situation in favour of independence, despite it being more than a year until polling day…

In an interview with The Scotsman, Mr Silver said polling data was “pretty definitive”. “There’s virtually no chance that the Yes side will win”, he said. “If you look at the polls, it’s pretty definitive really where the No side is at 60-55 per cent and Yes side is about 40 or so.

In this, Silver is on the side of the vast majority of pollsters. The real insight is over the question of how the polls will change between now and the election:

Historically, in any Yes or No vote in a referendum, it’s actually the No side that tends to grow over time, people tend not to default to changing the status quo.

The No side is even more dominant with the younger voters, so there’s not going to be any generational thing going on.

But Silver’s track record in British politics is not as stunning as his perfect prediction in the 2012 US presidential elections. He may have called all 50 states and DC correctly last year, but in 2010, when he tried to do similarly for Britain, he was well off the mark. As the Guardian‘s Oliver Burkeman reported in 2010, under the headline “Baseball nerd who predicted Obama’s win foresees Labour meltdown“:

Silver’s method breaks up the monolithic uniform swing and instead assigns specific percentages of the parties’ votes in 2005 to other parties in 2010. Using a recent polling average of the three main parties – with the Conservatives on 34%, the Lib Dems on 29.1%, and Labour on 26.9% – the differences between the two methods become stark. Using uniform swing, those percentages translate into 253 Labour MPs, 271 Conservatives, and 93 Lib Dems. Using Silver’s method, Labour ends up with just 214, with the Conservatives surging to 304, and the Lib Dems on 101.

Silver was actually spot-on with the Conservatives, who did indeed win 304 seats. But what he failed to call was the collapse in Lib Dem support. Not only did they not get 29.1 per cent of the vote – they dropped back down to 23 per cent by the time of the election – they actually scored fewer seats than they had in 2005. And all that difference went to Labour, who ended up with 258 seats.

Silver under performed in Britain partially because our polling data is far too different from the way our elections are actually run. In the US, where it is possible to accurately poll each of the states independently, a perfect opinion poll would perfectly call the election. But in the UK, such polls are nearly always national, and so can never truly capture the way elections play out on a local level. By and large, quirks cancel out, so that for every surprise Labour victory, there’s a surprise Tory one. But not always.

Still, the main reason why Silver was wrong in Britain was simply that public opinion shifted. Cleggmania didn’t make it to the polls, the Lib Dem share collapsed, and Labour swept up the leftovers. It wasn’t just Silver who got that wrong: most political pundits didn’t see it coming either.

So maybe the Yes campaign can breath a sigh of relief. It’s not over just because the baseball nerd sang.