European sovereign debt crises: Please read the following excerpt from an article: "Greece$$s financial crisis worsened Thursday. Moody$$s downgraded its bond ratings on Greek debt. This after the European Union$$s statistics agency revealed Greece$$s deficit is wider than expected. The IMF chief termed the developments $$serious$,$ adding there$$s no $$silver bullet.$$ The markets reacted sharply to the news: Yields on $2-$year Greek debt topped $10\%$ for the first time since $1999,$ the euro approached a $1-$year low vs$.$ the dollar and a global stock selloff spilled over in the U$.$S$.$ markets. Representing just $2\%$ of euro$-$zone GDP$,$ the problem is not that Greece is $$too big to fail$$ but that it is too interconnected to fail, as Aaron and Henry discuss in the accompanying segment. If Greece were allowed to default on its debt $($a remote but not impossible scenario$)$ it would call into question the long$-$term viability of the euro and, more immediately, raise more concern about Europe$$s other so$-$called PIIGS: Portugal, Ireland, Italy and Spain.

Hobbled by exorbitant borrowing costs, Greece triggered an emergency aid plan Friday to draw cash from the International Monetary Fund and countries that use the euro $$ the first test of whether the EU is prepared to bail out one of its members. The package has enough money to keep Greece from defaulting on its massive debts anytime soon. But Athens still faces years of painful cutbacks and questions about its long$-$term finances, raising worries that its troubles will affect other indebted members of the European Union and further harm the euro currency. The Greek debt crisis escalated sharply Thursday, weakening the euro and sending ominous ripples across a stagnant European economy. Greece is on the edge of default as talks continue on a $$56$ billion rescue package from the International Monetary Fund and the European Union that is contingent on Athens taking further austerity measures. Even if the government agrees to more cuts, the rescue continues to face strong opposition from Germany, where the public fears it will have to shoulder an unfair burden in a bailout."

Greek bond yields had risen due to higher default risk on these bonds. How is this related with the Maastricht criteria? In other words, is this outcome a result of the violation of the Maastricht criteria? What would you expect to see on German bond yields in the future if this situation persists? Is this a general problem with fixed exchange rate systems?