So, to be an optimal currency area it is necessary that interest rates, as determined by the Taylor Rule, are desirably the same in all areas of that currency zone.
The chancellor also appeared to rule out proposals suggesting Germany should act to curb its trade surpluses with other euro-zone economies as a way to address the big financial imbalances inside the currency area.
Another big task is meeting European Union worries about the rule of law, which are holding up Romania's accession to the Schengen passport-free travel zone.