The article discusses how countries in a currency union face risks of default and currency fluctuations. The researchers created a model to study a small country's situation in a currency union, where the government spends too much and can't pay its debts. They found that market expectations of a change in policy lead to default and currency risks. The study shows that during the Greek crisis from 2009 to 2012, about a quarter of the yield spreads were due to currency risk.