Here's the price of 10 year Greek bonds, starting on December 22 2009 when Moody's downgraded it to A2. Today, that last datapoint, they downgraded it to A3. In between, the price of their bonds went from about 100, to 84. I suppose somewhere around 50 it will be downgraded again!
Sometimes you wonder if almost everyone in finance simply tells people merely what happened last year.