Tiffany & Co. and Blue Nile have slipped in their ratings with Merrill Lynch from “neutral” to “sell”, reports CNBC.com. The Merrill Lynch analyst Lorraine Maikis said that the dip in sale of jewellery has reduced earnings for the two retailers. The dip has bee influenced by the economic slump in the US and rising costs of everyday necessities like fuel, food, weak credit and housing markets and soaring precious metal prices. Tiffany was also analysed by the Oppenheimer Funds analyst Roxanne Meyer, as “Perform” from “Outperform”.