In relation to the inadvertent political consequences of the United Kingdom leaving the European Union, the Irish economist and author David McWilliams makes this interesting point in the Financial Times on the viability of a possible post-Brexit reunited Ireland:
[For the north of Ireland] The UK’s annual subvention is just over €10bn annually. When seen from the perspective of the North, with its total GDP of under €50bn, it looks like a significant figure — but when seen from the perspective of Dublin, it is not insurmountable. The usual way financial markets assess whether national expenditure and debts are sustainable is the debt/GDP ratio. Northern Ireland would cost less than 4 per cent of the Irish Republic’s GDP annually. Of course, even this manageable figure would end up lower because the combined Irish GDP of the Republic combined with the North would be well over €300 billion, reducing the subvention as a percentage of income yet more. In pure budgetary terms, there is little doubt that the Republic’s economy could absorb the North and this is before the commercial dynamism of unification kicks in.
And the above doesn’t even factor in the strong likelihood of continued financial contributions from the UK, as well as the EU and perhaps US, towards a post-unity Six Counties.