Hard to know Moody's mood

On Wednesday, Moody's Investors Service downgraded China's sovereign credit rating from Aa3 to A1, the first time in nearly 30 years, saying China's financial strength could erode in the coming years as its growth slows and debt continues to rise.

The Chinese government has never cared much about the outlook of rating agencies that use tinted glasses to assess the country's economy, but people should guard against their commercially motivated rating moves and their underlying logic.

Some researchers have even linked a certain rating agency's assessments to the subprime crisis in the United States.