Sure, no problem, Jose. The stability comes not only due to exchange rate (for instance the pound is traded higher than the euro, but no trustworty competitor if one looks at other dimensions including history), but rather due to low growth of consumer prices. In this article by Mundell (http://robertmundell.net/nobel-prize/ , table 2) you will see where in the world the prices are the most stable. Barry Eichengreen has also done research on it

(Eichengreen, B. 2005. Sterling's Past, Dollar's Future: Historical Perspectives on Reserve Currency Competition, National Bureau of Economic Research.

Eichengreen, B. 2010. Exorbitant Privilege: The rise and fall of the Dollar and the Future of the International Monetary System, Oxford University Press.

Eichengreen, B., et al. 1990. "One money for Europe? Lessons from the US currency union." Economic Policy: 118-187.)

Finally there is the homepage I quoted called "measuringworth.com".

A flexible exchange rate is at one end of Williamson's markets-hierarchies approach, namely at the left end, close to spot markets, i.e. low degree of institutionalization. In case money did not exist, everything would be barter and that would be a perfectly "flexible" exchange rate (this happened in the past). Since then we have progressed. Chunks in the sense of Herbert Simon have become larger, tending toward ever higher degrees of institutionalization, and standardization occurred in measurements, be it weight or dimensions, so one can better compare, for instance the price for two fish, with the notion of "pound" or "foot" coming from there. Since Napoleon, the metric system has dominated and has a clearly claim towards universality as it is accepted by physics (cf. the "International System of Units"/SI).

What I said was that Germany has no own currency but that it shares its currency with neighbors. The point is of course that meter or kilogram are objectively measurable, whereas "utility" has a subjective component. Therefore human beings have in the year 2014 not managed to agree on one world currency that replaces all others. To use again Herbert Simon, this reflects a lack of optimality, instead evoking "satisficing". Differential development is universal, and not restricted to the eurozone, so in case the Dutch have a significantly higher GDP/person than the Czech, this is no different from an average person in "District of Columbia" being richer than an average person in "Missisissippi", likewise for aggregates with the largest GDP being California/Germany. Actually, this is fractal, as wealth is unevenly distributed between the "Laender" in Germany, and within the same city too and so forth. Also currency is just one aspect that the EU stands for, with Schengen and many other aspects of integration belonging to it and having changed our lives, too, to the better, IMHO. The economic notion that can explain some of the major advantages is the reduction of transaction costs. The OCA framework clearly has its merits and its limitations, but picking one country for accusations does not hold water when wages inside that country are not even homogeneous (and again, they are nowhere on our planet) and when no "central decision maker" is there, either. To claim that that country prevents the return to equilibrium conditions is short term thinking and shows a lack of awareness of the global arena. Germany alone cannot solve the Ukraine crisis, but when the Europeans communicate with one another enough (just as in the panopticon puzzle), they can show that the core is empty and the "aliens/central decision maker" never existed in the first place. As a last reading recommendations, feel free to check out, "Jonung, L. and E. Drea (2009). The Euro--it Can't Happen, It's a Bad Idea, it Won't Last: US Economists on the EMU, 1989-2002, European Commission, Directorate-General for Economic and Financial Affairs.". We are currently in the FOURTH phase.