Why, then, is the United States able to operate with a single currency, despite major differences among its 50 states? There are three key economic conditions – none of which exists in Europe – that allow the diverse US states to operate with a single currency: labor mobility, wage flexibility, and a central fiscal authority.
此外，单一货币制度还弱化了市场信号，使得财政赤字过度膨胀的国家得不到警告。而当一国的财政赤字过大从而需要增税和削减政府开支时——正如眼下希腊的情况，由此造成的GDP和就业萎缩无法通过货币贬值、增加出口和减少进口来缓和。