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 March 14. National Penn Bancshares ( NPBC) is the holding company for National Penn Bank, which provides commercial banking services in southeastern Pennsylvania and Maryland. It has been upgraded to buy. Shares have risen at a faster pace than the S&P 500 in the past year, and we still see upside potential. For the fourth quarter, net income increased 2.1% $16.7 million, and revenue grew 9.8% to $107 million. The company's gross profit margin is high at 54%, but its net profit margin of 16% trails the industry average. For 2008, the market is predicting a contraction of 1.6% in full-year earnings per share to $1.29 vs. $1.31 in 2007. National Penn Bancshares had been rated hold since June 29. Microchip Technology ( MCHP), a maker of semiconductor products, has been upgraded to buy. For the fourth quarter of fiscal 2008, revenue increased 0.6% to $252.6 million, and earnings per share rose to 38 cents from 33 cents. Return on equity increased to 30% from 16% in the same period. In addition, net operating cash flow rose 23 % to $132.1 million year over year. The company's debt-to-equity ratio of 0.99 exceeds the industry average, but its quick ratio of 8.78 is very high and demonstrates very strong liquidity. Microchip Technology's gross profit margin is very high at 70, and its net profit margin of 31.70% compares favorably to the industry average. Microchip Technology had been rated hold since Nov. 12. AutoDesk ( ADSK), a design software company, has been downgraded to hold. Robust revenue growth, a solid financial position and expanding profit margins are countered by a disappointing stock-price performance. For the fourth quarter, revenue rose 20% year over year to $599.1 million, but earnings per share remained flat at 40 cents. The company has no debt to speak of and a quick ratio of 1.79, which demonstrates an ability to cover short-term liquidity needs. Net operating cash flow has increased 15% to $219 million over the year-ago quarter. Despite this increase, Autodesk is growing at a significantly lower rate than the industry average of 106 %.