Each weekday, TheStreet.com Ratings updates its ratings on the stocks we cover. Our model projects a stock's total return potential over a 12-month period, including both price appreciation and dividends. Our buy, hold or sell ratings designate how we expect these stocks to perform against a general benchmark of the equities market and interest rates.While our 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. Some recent rating changes are highlighted below. Georgia-based banking firm GB&T Bancshares ( GBTB) has been downgraded to a hold from a buy. The company's stock price has declined 14% over the past 12 months. TheStreet.com Ratings sees little in GB&T's numbers to suggest that the trend will be reversed in the coming year. The company had been rated a buy since March 2005. TrustCo Bank ( TRST) has also been downgraded to a hold from a buy. The company operates bank offices in New York, New Jersey, Vermont and Florida. TrustCo's revenue grew just 8.9% in the fourth quarter of fiscal 2006 compared with the same quarter a year ago. Revenue throughout the industry grew by an average of 50.8% during that same period. The company's stock price slipped 21.5% over the past 12 months. TrustCo had been rated a buy since December 2006.