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.

Polaris

(PII) - Get Report

has been upgraded to a buy from a hold. The company makes all-terrain vehicles, snowmobiles and motorcycles. The company's return on equity in the fourth quarter of fiscal 2006 was 67.4%, more than 10 times the industry average. Net operating cash flow also shot up 47.5% in the latest quarter compared to the same quarter a year ago. In spite of those strengths, the company's earnings per share have shown a pattern of decline over the past two years. However, TheStreet.com Ratings expects this trend to reverse going forward. Polaris had been rated a hold since January 2007.

MAF Bancorp

(MAFB)

has been downgraded to a hold from a buy. The company conducts banking business through branches in Illinois and Wisconsin. MAF Bancorp's revenue growth has lagged the industry average. Return on equity also fell to just 7.9% in the fourth quarter of fiscal 2006 compared with 10.6% in the same quarter a year ago. The company had been rated a buy since April 2006.

Medical diagnostic product manufacturer

Inverness

( IMA) has been upgraded to a buy from a hold. The company's products include over-the-counter pregnancy and fertility tests. Inverness' EPS grew 155.6% in the fourth quarter of fiscal 2006 compared with the same quarter a year ago. The company's stock price has also enjoyed sizable gains over the past 12 months, a trend TheStreet.com Ratings expects will continue. Inverness had been rated a hold since March 2005.

Discount retailer

Fred's

(FRED)

has been upgraded to a buy from a hold. Revenue rose 17.3% in the fourth quarter of fiscal 2006 compared to the same quarter a year ago. Average revenue growth throughout the industry was just 5.4% during that same period. Fred's debt-to-equity ratio is just .01, suggesting there has been very successful management of debt levels. The company had been rated a hold since March 2005.

Biotech firm

Amgen

(AMGN) - Get Report

has been downgraded to a hold from a buy. The company's return on equity fell to 15.6% in the fourth quarter of fiscal 2006 compared with 18% in the same quarter a year ago. Amgen's stock price has tumbled 20.3% over the past 12 months. The company had been rated a buy since October 2006.

Additional ratings changes are listed in the table below.