Scottish independence: What have the polls been saying?
With now just a year to go to polling day, Scotland's referendum campaign has certainly heated up so far as opinion polling is concerned.
In the two months to the end of July, there were no polls at all on how Scotland intended to vote in referendum. In the last two months, in contrast, nine polls have been published, with most of these being unveiled during the last two or three weeks.
At first glance the picture they have presented has been very confusing. One poll put the Yes side one point ahead, while another suggests they were no less than 32 points behind.
But this apparent volatility tells us more about the pollsters than it does about the voters. There are some important differences in the way in which the recent polls have been conducted and reported and these help to account for much of the variation between them.
If we compare what each poll is saying now with what the equivalent poll was saying earlier this year - or indeed last year - we find that for the most part their figures have changed remarkably little.
That means what is probably the best measure of the balance of public opinion - the average ratings for the Yes and the No side across all of the recent polls - looks much the same now as it did a year ago.
The Yes side's average poll rating currently stands at 33%, while the No side has a score of 50%. Around 17% say they do not know or are unsure about what they will do.
If we leave the Don't Knows to one side, that suggests that if the referendum were being held today rather than next year, 60% of people would vote to stay in the United Kingdom while 40% will vote for Scotland to become an independent country.
That is a little better for the Yes side than the equivalent figures for those polls that were conducted earlier this year, which on average gave Yes 38% and No 62%.
But they are virtually the same as the average figures across all of the polls conducted last year, which put Yes on 41% and No at 59%.
We perhaps should not be surprised that it is proving difficult for both sides to secure a decisive change in the balance of opinion. For in part people's views are a reflection of their sense of identity, that is whether they feel Scottish or British - and people do not change their sense of identity very easily.
According to an Ipsos-MORI poll earlier this year, 56% of those who say they feel Scottish, not British propose to vote Yes in the referendum compared with just 13% of those who feel British and not Scottish.
Still, far more people feel strongly Scottish rather than strongly British, so clearly people's views are not just a reflection of their identity. Otherwise the Yes side would be well ahead in the polls.
What is also shaping people's views is what they think the practical consequences of independence would be - and above all the economic implications for themselves and their family.
A recent ICM poll asked people how they thought they would vote if they were convinced that they would be £500 a year better off. As many as 47% said that in those circumstances that they would support independence while only 37% indicated that they would oppose it.
Conversely, only 18% would support independence if they felt they would be £500 a year worse off, while no less than 60% would be opposed.
So, who wins the referendum could well turn on who wins the economic argument. Unfortunately for the Yes side, at the moment it appears that more people think that independence would be bad for Scotland's economy than believe it would help bring about economic success.
If that were to change, however, the level of support for independence could do so too.
At the same time many people seem to be uncertain about what the consequences of independence would be. According to the most recent Scottish Social Attitudes survey no less than 58% feel unsure what would happen.
Such feelings seem to be holding some people back from supporting independence. This appears to be especially true of women. So if people do come to feel rather clearer in their minds about what independence would entail then maybe that might see the balance of opinion change too.
Although at 18% those who say they Don't Know what they will do are not particularly numerous, they too could still help to tip the balance of opinion. Some polls have tried to get the "Don't Knows" to say what they think they might do, and this evidence suggests the Yes side might have the better chance of picking up a majority of their votes.
Meanwhile, although at the moment it appears that a majority of Scots are not in favour of independence, there is considerable evidence that a majority would like the existing devolved parliament to be more powerful, taking on more responsibility in particular for taxation and welfare benefits.
At present the three main pro-Union parties, Labour, the Conservatives and the Liberal Democrats, are at various stages of coming up with plans for more devolution. But if they fail to convince voters that Scotland will get more devolution if it votes No then, according to ICM at least, some No voters might switch sides, thereby making the race tighter than it currently is.
So the polls may not have moved much so far. But the important arguments and debates that will take place in the next 12 months could still make a difference.
- John Curtice is Professor of Politics at Strathclyde University, and Chief Commentator at whatscotlandthinks.org