After Croatia, who's next for the euro?

The euro, once seen as the next great step in the European project, has undergone a tumultuous and fraught existence since its inception in 1999. Following the currency's debt crisis in 2009, the economies of Greece, Spain, and Portugal were shaken to their core. The euro's very survival came under threat. Only through the joint commitment and perseverance of its member states did the currency survive.

However, with its survi...