The latest monthly ICM poll for Scotland on Sunday, published today, will do little to smooth the worried brows in the No camp. Once again the message appears to be that the referendum race has become, from their perspective at least, all too close for comfort.

The poll puts Yes on 39%, No on 46%. That represents a two point increase in the Yes vote compared with four weeks ago, while the No vote is down three points.

Once the Don’t Knows are excluded, the poll translates into a two point increase in the Yes vote to 45%. However, support for independence is still marginally lower (by one point) than it was in January when ICM registered what was at that time an all time high Yes vote (once Don’t Knows were excluded).

Thus today’s poll is best read as further evidence that the No lead continues to be rather narrower than it once was (ICM put the Yes vote at just 40% last September) but that (even bearing in mind last week’s Panelbase poll) it would as yet be premature to claim that the No lead has narrowed yet further in recent weeks. We would need to see increases in the Yes vote in polls produced by companies such as YouGov and TNS BMRB that have not polled for a while before we could be sure of that.

Still, as ICM are one of the pollsters producing relatively favourable results for the Yes side (if not necessarily as favourable as Panelbase), that still means the reported lead in today’s poll is quite a narrow one.

An invaluable and unique feature of the ICM poll is that it is regularly tracking voters’ attitudes towards some of the key issues in the independence debate. It is here that the No side would seem to have particular cause for worry.

As we have repeatedly said, nothing is more important than perceptions of the economy when it comes to whether voters end up in the Yes or No camp. Indeed, according to ICM’s latest poll, no less than 88% of those who think the economy would be good for the economy say they will vote Yes, while 92% of those who reckon it would be bad indicate they propose to vote No.

The past few weeks have seen a plethora of pronouncements from companies advising their shareholders of the risks of independence as they see them. Yet voters are apparently now less pessimistic about the economic consequences of independence than ever before.

While those who say independence would be bad for Scotland’s economy still outnumber those who claim it would be good by 43% to 38%, the five point gap is the smallest it has been yet. Last month it stood at 11 points, and last September at no less than 17.

If Scotland is to vote for independence there will almost undoubtedly have to be more optimists than pessimists by September. But the Yes side has evidently made some progress towards that objective, despite – or perhaps because – of the noises from the city and from industry.

Meanwhile, although people’s views about whether an independent Scotland would be a more equal society matter less in determining whether they are Yes or No voters, it seems that voters are increasingly warming to that nationalist tune too.

According to ICM, no less than 36% think that there would be less inequality in an independent Scotland, while just 16% believe there would be more. The resulting positive gap of 20 points, is six points up on last month and 13 points on last September.

Perhaps of particular note is the fact that rather more of those who voted Labour in 2011 say there would be less inequality (27%) than more (22%). Indeed, more generally the poll confirms the degree to which Labour support is potentially the weak link in the unionist camp; once the Don’t Knows are excluded no less than 34% of those who backed Labour in 2011 say they will vote Yes.

Labour’s efforts at its Scottish conference this weekend to bolster what it sees as the social justice case for the Union are evidently badly needed.

As well as asking people what they think independence would bring, ICM’s poll has also been tracking how people feel about more devolution in the event of a No vote. At 68% the proportion who think that the Scottish Parliament should become primarily responsible for taxation and welfare is at its highest level yet.

But a new question in today’s poll suggests there is widespread scepticism that that is what would happen. Just 39% – including just 50% of No voters and 42% of those who back the devolution of taxes and welfare – think Holyrood would be given more powers in the event of a No vote. (There are also not dissimilar findings, albeit in response to what was perhaps a less satisfactory line of questioning, in the latest release of findings from the Panelbase/newsnetscotland.com poll.) Evidently between them the unionist parties still have much work to do to persuade voters that they would in fact deliver.

Fortunately for them, an increasing proportion of No voters who believe in more devolution say they are determined to vote against independence even if they were to conclude that more devolution would not in fact happen. Four out of five are apparently of that view. But the 10% who say they would vote Yes and the additional 10% who say they do not know what they would do could still be more than the No side could afford to lose should the referendum race get much tighter.