I guess it depends which side of the fence you stand
If you are Scottish and pro independence you make the argument that being a member of the Union is holding your nation back economically.
If you are pro-union you make the opposite argument
It’s hard to prove, one way or another, until you jump through the hoop.
Personally I think NI is more likely to secede - but if it does pressure will mount for Scottish independence.
Personally, I hope they do.
I take this issue personally, because it outrages me that a minority settler population has held sway for so long, and with such vituperative hatred for, and contempt of the human rights of, the minority of indigenous Irish nationalist people they have colonised. All out of a sense of religious entitlement, and ethnic superiority.
The DUP, of which Nigel Dobbs MP is a leading member (he lost his seat last Thursday to a Sinn Féin opponent), supported apartheid South Africa, and even bought illicit missiles from the racist SA government to use against the Republicans waging a legitimate struggle for independence and deliverance from British oppression.
Good riddance, say I. And more like him should go, the sooner the better.
Of course the two sides will try to argue such - but the arguments are not, in fact, symmetrical - since Scotland, Wales and NI have actually been in the union for centuries.
If limited to good evidence and sound reasoning, unionists can argue that independence might in future imply more, or different problems for these economies, but not that existing weakness is a reason to maintain the union.
How unusual, a link to a Guardian piece from Geof, 
I’m happy to receive recommendations for a better English newspaper Timothy - or French (current favourite l’Humanité!).
Better or one that offers a different perspective? 
Better - of course.
To me what matters is truth and accuracy in reporting. The Guardian is owned by a not-for-profit trust constitutionally committed to decent standards of journalism - most other options are owned by foreign billionaires or tax-exiles with obvious political agendas.
You might be interested to know that I generally do NOT agree with the political editorial line of The Guardian - I read it simply because it is less biased than alternatives.
You might also find this interesting:
Pretty much my stance as well, though I am getting more left wing these days.
You might be on the same journey as me Paul. I was pretty centrist - although I was in the Labour Party at one time, I was a supporter of the ‘New Labour’ project, so guess you could say I was on the ‘right’ of Labour - and I even voted for Alan Beith - LibDem - once (although it was tactical more than whole-hearted).
It was the emerging knowledge of climate/ecological breakdown that radicalised me. The political centre simply doesn’t have a handle on this - its fundamental philosophy is ‘things are not too bad, capitalism is OK, it just needs its worst edges rubbing off’ - but this simply is not now a tenable position for anybody that believes in evidence-based policy-making. We have to make really radical changes to our economies and lifestyles - so there is literally no option other than political radicalism.
I think the CV pandemic will change the work patterns and lifestyles of millions without the need for political upheaval. Whether those changes will be enough for you Geof is of course a different matter. 
The real question is whether any changes will be enough for the planet!
One lesson that could be learnt from the current crisis - though I doubt if most politicians will learn it - is that there is no need, after all, for a gradual approach to change.
I used to fear that the implications of a real ‘green new deal’ would be extremely socially disruptive - but the fact is that people will accept a closedown of economic activity, that governments can mitigate its effects - that something like Universal Basic Income to protect a decent standard of living while facilitating a change of economic direction is perfectly possible…
