What’s the main idea of the news item? [originaltext] (27)This week, Moody’s

(27)This week, Moody’s Investors Service lowered its credit rating for Japanese government debt. The credit rating agency downgraded Japan one step from Aa2 to Aa3. Finance Minster Yoshihiko Noda said trust in the economy "will not be shaken" by Wednesday’s action. Moody’s said it acted because of Japan’s large budget deficits and buildup in government debt since the two thousand nine global recessions. Japan’s public debt is twice the size of its economy. Japan is the world’s third-largest economy.(28)Moody’s said another reason was Japan’s political situation. Japan has had five Prime Ministers since two thousand six. The current Prime Minister, Naoto Kan, is expected to resign soon.