So it has created a pessimal currency area, offering the worst of both worlds.
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The past decade, though, has also exposed Europe's weaknesses as an optimum currency area.
This would have an impact on the other 16 nations in the eurozone single-currency area, it warned.
Even more oddly, Mr Mundell believes that the planet as a whole is an optimal currency area.
In establishing the common currency area, the Euro, the separate countries are essentially throwing away this adjustment mechanism.
The resulting "optimum currency area" theory boils down to a handful of tests.
If left to run, that crunch will eventually rip the currency area apart.
Quite simply because it has been imposed on something which is not anywhere close to being an optimal currency area.
Oddly, however, Mr Mundell very strongly believes that Europe is, in practice if not in theory, an optimal currency area.
The end is that yes, fiscal transfers are indeed the only way in which a single currency area can be kept together.
And the unfortunate thing is that even that second solution would still take decades upon decades to actually create and optimal currency area.
Most analysts and investors agree Greece's remaining debt won't be repaid in full, whether it stays in the currency area or leaves it.
The big question is, how large do those fiscal transfers have to be in order for such a single currency area to work?
This would help advance the Lisbon Agenda and foster the deeper economic integration necessary to make the euro zone a sustainable currency area.
Economists who have looked at Europe, asking, in the manner of Mr Mundell, whether it is an optimal currency area, usually answer No.
The September figures show exports to the single currency area have now started to fall - they were down 0.2% on the month.
Bailouts for Spain and Italy might be required, dwarfing the cost of keeping Greece in the euro-zone fold and possibly fracturing the currency area.
Something very close to this is necessary, in the IMF's view, to manage this and future crises and build a stable single currency area.
And for a common currency to work it must be applied across something which is at least close to being an optimal currency area.
But Thursday's data means that the 17 countries of the single currency area have not expanded as a group since the autumn of 2011.
It makes no sense to have a lot of exchanges in a single currency area, because they disperse liquidity and keep trading costs high.
First, it makes the job of the European Central Bank difficult, because the bank has to set interest rates for the whole single-currency area.
The strong euro undermines the competitiveness of European exporters, and also drags down inflation in the single currency area due to the cheapening of imports.
EMU, its interest rates would be set by the European Central Bank, which would be guided by the inflationary outlook in the whole single-currency area.
Mario Draghi hinted last week that if leaders could credibly commit to tougher budget rules within the single currency area, "other things might follow".
Within the single-currency area competitiveness has to be regained the hard way by pushing down domestic costs or increasing productivity rather than the easier-to-swallow medicine of devaluation.
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But in a rapidly fragmenting currency area, it is well-nigh impossible.
Now, the sense among many investors is that the acute phase of the crisis is over and that the single currency area has turned a corner.
The basic background is that for such a single currency to work it is necessary for there to be fiscal transfers across regions within the currency area.
An optimal currency area would require convergence on monetary, fiscal, exchange rate, and political policies, which in turn would lead to productivity and growth rate convergence, explained Roubini.
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