When turmoil enveloped the globe three years ago, Poland's zloty declined against currencies seen as safer, including the euro. That made Polish exports less expensive for buyers abroad and helped keep the economy growing. Since then, Poland has been the sole member of the European Union to avoid a recession.

Support from the zloty isn't the only reason for Poland's success. But, coupled with the debt crisis rattling the euro zone, it has changed minds about adopting the euro