A single currency is not a guarantee that poverty or inequality will end globally. If this was the case every European would have been rich like Germany, England and France. But we have European countries like Greece that are going through a lot of economic problems. Poor nations will still remain poor even with a single currency policy. There are many nations which have adopted dollars as their currency, yet they are still not as prosperous as the US.

Having a single currency will only be possible if all the nations of the world are under one political arrangement. The Euro is used by many nations because they are united under a political organization called the European Union. It will be ve difficult to bring many nations under one political setup considering the level of confrontation or antagonistic position that exists between nations. An example is the proposed BRICS currency that has not materialized because each nation has a personal agenda.

It is noteworthy to state that each country has different economic conditions which require particular policies.  A single currency might not allow nations to make economic decisions that suit their economic conditions. Economic policies of developing nations might not suit a single currency.

A single currency I not the solution to poverty because rich nations will still have more of the currency while poor nations will have less. Which means the imbalance or inequality will still persist.