If only people had actually listened to what Mundell actually said / wrote:

> The four often cited criteria for a successful currency union are:[6]

> * Labor mobility across the region. […]

> * Openness with capital mobility and price and wage flexibility across the region. […]

> * A risk sharing system such as an automatic fiscal transfer mechanism to redistribute money to areas/sectors which have been adversely affected by the first two characteristics. […]

> * Participant countries have similar business cycles. When one country experiences a boom or recession, other countries in the union are likely to follow. This allows the shared central bank to promote growth in downturns and to contain inflation in booms. […]

* https://en.wikipedia.org/wiki/Optimum_currency_area

* https://www.jstor.org/stable/1812792?seq=1

In 2012 Krugman laid out three things that needed to be done to make the Euro work better:

* https://www.journals.uchicago.edu/doi/full/10.1086/669188#_i...