Euro a lapse of banking?

Paul Krugman, professor of economics at Princeton University and Nobel laureate, believes that countries that preferred to keep their own currency instead of adopting the euro are enjoying economic advantages: "One of the great lessons of the euro crisis is that Milton Friedman was right "when explaining the importance of exchange rates in Europe, says Krugman.
the Princeton professor says in his blog on the New York Times that" many economists remain deeply convinced that the euro has not affected when facing the crisis ...
the large wage and price adjustments in the euro countries, have been much easier in countries that have faced depreciations of their currencies (deflation relative) ". Milton Friedman was right, the exchange rate plays a key to correct imbalances between countries without excessive suffering paper.
A case exemplified some economists to justify that the euro has not been a hindrance is the 'miracle' of Ireland.
The economist Thordvaldur Gylfason compares the crisis of the 'Celtic Tiger' with Iceland, arguing that although Reykjavik maintained its national currency, both countries have recovered their levels of income per pre-crisis almost on par capita.
Differences between Ireland and Iceland
However, Krugman points out that everything is not income per capita. If the labor market data are observed, it can be seen as the employment rate in Iceland has recovered and surpassed pre-crisis levels, but Ireland is still well below the levels of 2007. The employment rate is the ratio between the employed and the population of 16 years to 64 years to make the calculation with the methodology used by Eurostat. 
This data suggests that although Ireland's GDP is growing strongly, the labor market still has not regained health he enjoyed in 2007, when the employment rate was 70%, while 63.1% now. In Iceland , the employment rate is today 85%, while in 2007 it was also 85%.
"I guess and understand the urgency justify the creation of the single currency. But the evidence suggests that there are significant economic benefits for countries that decided to maintain its own currency ", says Paul Krugman.