Rating agencies plays a very important role in stock market & the decision making of the investors.The role of rating agencies is to rate the countries, organization & Banks according to the financial & debt position.
The investors sentiment is very much related to these ratings agencies if they downgrade their rating for these economy & organization then investors want to take out their money from the market and if they keep the rating unchanged or upgrade the rating then at that time Investors becomes ready to invest.AS some days before different credit rating agencies downgrade different banks and countries of the world for the investment purpose then most of the indices go in the downward direction.
According to me these rating are not always very perfect because rating given by these companies depends
on many aspects & parameters. So, if one aspect of the country or organization is not good then it may happens other aspect is very good.