SG Equity Research said in a research note today that it had downgraded the stock of SABMiller to "underperform" from "hold". The note said the move had been made because of concerns over a lack of disclosure at the firm. SG's analyst James Williamson said: "Given SABMiller's lack of disclosure relating to the financial position of its holding company, we do not feel comfortable giving the company the benefit of the doubt with our valuation."