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 forecasted company earnings. Objective elements include volatility of past operating revenue, financial strength and company cash flows. TheStreet.com Ratings has initiated coverage of independent power producer Mirant ( MIR) with a hold rating. The company's stock price has shot up 95.8% in the past twelve months. Net operating cash flow more than doubled in the first quarter of fiscal 2007 when compared to the same quarter a year ago. On the other hand, earnings have deteriorated during that same time period. Mirant lost 52 cents per share in the most recent quarter after earning $1.37 per share in first quarter of 2006. Oil and gas contract driller Union Drilling ( UDRL) has been upgraded to a hold from a sell. The company has demonstrated a pattern of positive earnings per share growth over the past two years. TheStreet.com Ratings expects this trend to continue. Union Drilling is in a solid financial position with reasonable debt levels by most measures. The company had been rated a sell since December 2006.