Tyler Cowen explains:
If Germany and a few other, smaller AAA countries were to guarantee or monetize the debts of Italy, Spain, and possibly France and Belgium, never mind Greece and Portugal, Germany would not be AAA itself. The German median voter has very little interest in guaranteeing the above-mentioned debts. If German yields are flipping upwards, it is, in my view, because investors now see the whole euro deal as unraveling and don’t want to deal with the complexities and flak. A big chunk of the German auction didn’t sell at all. You don’t have to think that Germany is ripe to default to see that markets are warning Germany not to take on the whole burden.
The only remaining question, if Germany isn’t willing to take on the entire burden of European debt, is when will the whole edifice come crashing down and who’ll manage not to be crushed by falling debris.
