Each business day, 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. However, the rating does not incorporate all of the factors that can alter a stock's performance. For example, it doesn't always factor in recent corporate or industry events that could affect the stock price, nor does it include recent technology developments and competitive dynamics that may affect the company. For those reasons, we believe a rating alone cannot tell the whole story, and that it should be part of an investor's overall research. The following ratings changes were generated on Thursday, July 3. First up is AstraZeneca ( AZN), which was upgraded to buy from hold. The company develops, manufactures and markets prescription drugs, biologics and vaccines in the areas of cardiovascular, gastrointestinal, neuroscience, oncology, respiratory and inflammation and infection worldwide. Despite its quarterly revenue growth, the 10% year-over-year growth underperformed the industry average of 12%. Its gross profit margin is currently very high, coming in at 90%, having increased from the same quarter the previous year. Regardless of the strong gross profit margin results, the net profit margin of 19% trails the industry average. Net operating cash flow has slightly increased to $2.39 billion, or by 9% when compared to the same quarter last year.