Each weekday, TheStreet.com Ratings updates its ratings on the stocks it covers. The proprietary ratings model projects a stock's total return potential over a 12-month period, including both price appreciation and dividends. Buy, hold or sell ratings designate how the Ratings group expects these stocks to perform against a general benchmark of the equities market and interest rates. While the ratings model is quantitative, it uses both subjective and objective elements. For instance, subjective elements include expected equities market returns, future interest rates, implied industry outlook and company earnings forecasts. Objective elements include volatility of past operating revenue, financial strength and company cash flows. Vina Concha a Toro ( VCO) produces and exports wine in Chile and internationally. It has been downgraded to hold from buy. The company demonstrated revenue growth of 45.9% in the second quarter of 2007 compared with the same period last year, and net income increased by 96.7% over the same period. It also shows expanding profit margins and a debt-to-equity ration below that of the industry average. As a counter to these strengths, the company has not displayed a clear earnings trend over the past two years. Vina Concha a Toro had been rated a buy since September 2006. Miner of palladium, platinum and associated metal Stillwater Mining Company ( SWC) has been downgraded to a sell from a hold. The historical performance of the company's stock has been generally disappointing, and its profit margins have been poor. Stillwater's net loss widened to $2.52 million in the second quarter of 2007 from $2.34 million a year earlier. T he company has reported somewhat volatile earnings recently, and TheStreet.com Ratings believe it is likely to report a decline in the coming year. Stillwater Mining Company had been rated a hold since November 2006.