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 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. AMB Property Corporation ( AMB) has been upgraded to a buy from a hold. Its EPS for the second quarter of fiscal year 2007 increased 91.22% over the year-earlier period, continuing a trend of positive EPS growth over the past two years. The company's net income rose 56.95% over the same period, outperforming the S&P 500 but lagging the industry average. AMB's stock price has increased by 7.75% over the last year, and still has good upside potential. AMB had been rated a hold since June 2007. Electro Scientific Industries ( ESIO) makes high-technology manufacturing systems for the global electronics market. It has been upgraded to a buy from a hold. Fiscal fourth-quarter 2007 revenue was up 23.9% on the year, and this growth appears to have trickled down to the company's bottom line. Electro Scientific's earnings per share rose 35% over the same period, continuing a pattern of positive EPS over the past two years. The company's net income increased 33.2% over the same time frame, exceeding both S&P 500 and the industry average. Its share price has grown 29.11% over the last 12 months and still shows upside potential. Electro Scientific had been rated a hold since April 2006.