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. Structural steel and steel bar products manufacturer Chaparral Steel ( CHAP) has been upgraded to a buy from a hold. The company's net income increased to $80.21 million, or 42.9%, in the fourth quarter of fiscal 2007, up from $56.14 million in the final quarter of 2006. While its revenue improved by 20.5% during the same period, it trailed the industry average of 36.4%. Chaparral Steel's debt-to-equity ratio of 0.32 is beneath that of the industry average, implying successful management of debt levels. Driven by earnings growth of 68.8% during fiscal 2007, the company's stock has increased by 141.7%, making it relatively expensive compared to the rest of its industry. TheStreet.com Ratings believes that the company's strengths justify the higher price levels. Chaparral Steel had been rated a hold since coverage was initiated in September 2006. Tyson Foods ( TSN), which produces, distributes and markets chicken, beef, pork, prepared foods and related allied products, has been upgraded to a buy from a hold. Net income swung from a loss of $52 million in the third quarter of 2006 to a profit of $111 million in the third quarter this year. Over the same period, EPS went from a loss of 15 cents per share in the third quarter of 2006 to a gain of 31 cents per share in the most recent quarter.