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 Feb. 21.

Susquehanna Bancshares ( SUSQ), a banking and financial services provider, has been upgraded to buy on strong revenue and high margins. In the fourth quarter, the company posted a year-over-year revenue increase of 25% to $193.8 million. Over the same interval, earnings per share fell to 27 cents from 41 cents. However, for 2008, the market expects full-year EPS of $1.52, up from $1.24 this year.

At 54%, Susquehanna's gross profit margin is high, but has decreased year over year. Its net profit margin of 9.6% trails the industry average. The company's return on equity has slightly decreased to 4% from 8.9% a year ago, underperforming sector peers. Susquehanna Bancshares had been rated hold since Aug. 1.

Knightsbridge Tankers ( VLCCF), a transporter of crude oil, has been upgraded to buy. Shares have climbed 16% over the past year on strong earnings. This stock still has good upside potential despite its impressive rise.

For the fourth quarter, net income increased 559% year over year to $60.4 million. Earnings per share rose to $3.53 from 53 cents over the same period. However, for 2008, the market anticipates a 61% contraction in annual EPS to $1.94. Return on equity greatly increased year over year to 38% from 26% and greatly exceeds the industry average. Gross and net profit margins are quite high at 71% and 249%, respectively. With a P/E of 5.64, the stock is cheaper than its industry peers. Knightsbridge Tankers had been rated hold since Aug. 15.

First Bancorp ( FBP - Get Report), a financial services provider, has been upgraded to hold. For the fourth quarter, the company posted a 1.3% year-over-year revenue drop to $305.4 million. Net income declined to $7.4 million, or a loss of 3 cents a share loss, from a profit of $22.3 million, or 14 cents a share, a year ago. The market expects an improvement in full-year EPS for 2008. At 30%, gross profit margins are currently lower than desirable, and the company's net profit margin of 2.4% significantly trails the industry average.

Shares have fallen 15% over the past year, underperforming the S&P 500, thanks in part to declining EPS. Looking ahead, we do not see anything in this company's numbers that would change this trend. Naturally, a bull or bear market could sway the movement of this stock.

Seaspan ( SSW - Get Report), a container shipper, has been downgraded to sell. In the fourth quarter, earnings swung to a loss of $20 million, or 35 cents a share, from a profit of $10.5 million, or 24 cents a share, in 2006. The company's gross profit margins are very high at 77%, but have decreased since last year. Its net profit margin of -36.40% significantly trails the industry average. Seaspan's debt-to-equity ratio of 1.55 exceeds the industry average. However, with a very strong quick ratio of 8.00, the company should be able to cover short-term cash needs. Seaspan had been rated hold since May 10.

Aegean Marine Petroleum ( ANW), a marine fuel logistics company, has been initiated with a hold rating. Shares have jumped by 94.96% over the past year, significantly outperforming the broader market.

Aegean's fourth-quarter revenue leaped by 150% from the year-ago period to $500 million. However, EPS declined 21% to 15 cents. This company has reported somewhat volatile earnings recently, but this year, the market expects an improvement in annual earnings to 70 cents vs. 66 cents in 2007. Aegean's gross profit margin is extremely low at 2.2%, and its net profit margin of 1.20% trails the industry average. With a P/E of 48.71, Aegean shares are more expensive than others in its sector.

Additional ratings changes from Feb. 21 are listed below.

Ticker Company Name Change New Rating Former Rating
FBP FIRST BANCORP P R Upgrade Hold Sell
GRIF GRIFFIN LAND & NURSERIES INC Upgrade Buy Hold
HIHO HIGHWAY HOLDINGS LTD Downgrade Sell Hold
VLCCF KNIGHTSBRIDGE TANKERS LTD Upgrade Buy Hold
LPSN LIVEPERSON INC Downgrade Hold Buy
SUSQ SUSQUEHANNA BANCSHARES INC Upgrade Buy Hold
TTIL TTI TEAM TELECOM INTL LTD Upgrade Hold Sell
SSW SEASPAN CORP Downgrade Sell Hold
GASS STEALTHGAS INC Upgrade Hold Sell
KAZ BMB MUNAI INC Downgrade Hold Buy
ANW AEGEAN MARINE PETROLM NETWK Initiated Hold
DBTK DOUBLE-TAKE SOFTWARE INC Downgrade Sell Hold
MPEL MELCO PBL ENTERTAINMENT-ADR Initiated Sell

This article was written by a staff member of TheStreet.com Ratings.