Fitch, the international ratings agency, downgraded Thursday – Buffett’s AAA credit rating Berkshire Hathaway (BRK-A) (BRK-B) to lowly AA because of possible stock and credit market losses. The Omaha-based insurance and electricity conglomerate has seen its shares lose more than 30% of their value YoY. Fitch’s downgrade consists on the large stakes Berkshire holds in publicly traded companies, such as Coca-Cola (KO) and American Express (AXP), as well as huge derivatives contracts that expose it to possible losses in the credit and stock markets. Remains to be seen if Moody’s (MCO) or Standard and Poor’s follow with their own downgrades.