Financial crises, credit ratings, and bank failures : emerging market instability - do sovereign ratings affect country risk and stock returns?
研究了主权债务评级和展望变化如何影响新兴经济体的债券和股票市场，发现评级变化在危机期间影响更强，且评级机构可能加剧市场不稳定。
Changes in sovereign debt ratings and outlooks affect financial markets in emerging economies. They affect not only the instrument being rated (bonds) but also stocks. They directly impact the markets of the countries rated and generate cross country contagion. The effects of rating and outlook changes are stronger during crises, in nontransparent economies, and in neighboring countries. Upgrades tend to take place during market rallies, whereas downgrades occur during downturns, providing support to the idea that credit rating agencies contribute to the instability in emerging financial markets.