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. BankAtlantic Bancorp ( BBX), which offers consumer and commercial banking services, has been downgraded to sell. The company has experienced a steep decline in earnings per share in the most recent quarter in comparison with its performance from the same quarter a year ago. Earnings per share have declined over the last two years, and that is expected to continue in the coming year. The change in net income from the same quarter one year ago has significantly exceeded that of the thrifts and mortgage finance industry average. The company has been rated hold since February 2006. Cabot Microelectronics ( CCMP), which makes chip-manufacturing materials, has been upgraded to buy. The company has reported revenue growth higher than the industry average in the most recent quarter, and revenue has increased by 14.2% since a year ago. It has a largely solid financial position with reasonable debt levels, reasonable valuation levels, solid stock price performance and expanding profit margins. TheStreet.com Ratings believes these strengths outweigh the company's subpar growth in net income. The debt-to-equity ratio is very low at 0.01 and is currently below the industry average, implying that there has been very successful management of debt levels. The company had been rated hold since June 6.