Credit rating agencies are involved in assigning rating scores to bonds, countries and other investments. The big three credit rating agencies are S&P Global Ratings (S&P), Moody's, and Fitch Group. S&P and Moody's are based in the US, while Fitch is dual headquartered in New York and London, and is controlled by Hearst. As of 2013 they hold a collective global market share of roughly 95% with Moody's and Standard & Poor's having approximately 40% each, and Fitch around 15%. Investigate and explain the factors used by the credit rating agencies in assigning ratings to different debt instruments