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 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 forecasted company earnings. Objective elements include volatility of past operating revenue, financial strength and company cash flows.

Consumer electronics manufacturer

Sony

(SNE) - Get SONY GROUP CORPORATION SPONSORED ADR Report

has been downgraded to hold from buy. The company's return on equity fell to 3.8% in the fourth quarter of fiscal 2006, significantly lower than the industry average. TheStreet.com Ratings feels Sony's gross profit margin of 6.5% is also extremely low. Sony had been rated a buy since February 2007.

Oil and gas explorer

Bronco Drilling

(BRNC)

has been upgraded to hold from sell. Revenue jumped 39.9% in the first quarter of fiscal 2007 compared with the year-earlier period. The company's 0.18 debt-to-equity ratio is very low.

At the same time, BRNC has a quick ratio of 2.2, which suggests it can cover short-term liquidity needs. The quick ratio compares a company's non-inventory assets with its liabilities. Bronco Drilling had been rated a sell since September 2006.

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Circuit board manufacturer

TTM Technologies

(TTMI) - Get TTM Technologies, Inc. Report

has been upgraded to buy from hold. The company's products are used in everything from airplane navigation systems to high-speed routers for corporate networks. Revenue jumped 143.4% in the first quarter of fiscal 2007 over the year-earlier period.

Meantime, the company's stock has tumbled 25.6% in the past year and is currently trading at a level where the price-to-earnings ratio is less than half the electronic manufacturing services industry average. TheStreet.com Ratings feels this is an attractive valuation level. TTMI had been rated a hold since March 2007.

Commercial and consumer finance company

CIT Group

(CIT) - Get CIT Group Inc. Report

has been upgraded to buy from hold. The company's revenue shot up 25.1% in the first quarter of fiscal 2007 compared with the year-earlier period. Net operating cash flow has increased 29.6% during that same period. CIT Group's stock price is up 13.8% over the past 12 months.

TheStreet.com Ratings feels there is still more upside potential left. CIT had been rated a hold since April 2007.

Some recent rating changes are highlighted below.

Editor's Note: An earlier version of this story said that Focus Media had been downgraded to a sell rating based on its stock's performance. That rating appears to be based on mistaken data.