NEW YORK (CNN/Money) - Edmunds.com, an automotive data Web site, will soon begin displaying 5-star depreciation ratings for cars.

The ratings are calculated by Automotive Lease Guide, a company that forecasts the resale -- or residual -- value of cars, information that is used to calculate lease rates for vehicles. The new star ratings provide users a way to compare how well cars can be expected to hold their value over time.

"The ALG Depreciation Ratings will enable consumers to easily compare vehicles based upon anticipated depreciation that considers current market conditions and prices, including incentives," said John Blair, ALG's chief executive officer.

Unlike the residual values ALG provides for use in the auto financing industry, which are based on the manufacturer's suggested retail price (MSRP), the figures underlying the star rating system are based on the "True Market Value" (TMV) for the new vehicle as calculated by Edmunds.com. The TMV is calculated to reflect actual prices paid by consumers.

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In this way, the star ratings can factor in rebates and dealer discounts. Depreciation figures based on MSRP would tend to show a steeper decline in value than figures based on actual transaction prices because the MSRP is generally higher than the transaction price.

"Retained value has become an important purchase decision in this era of incentives, and these ratings will be extremely useful for automotive purchasers," said Blair.

Designed for use by consumers, the star system is based on a ranking of vehicles by expected three-year depreciation. For example, the top 10 percent of vehicles were given 5-star ratings and the bottom 10 percent were given a 1-star rating.

The ALG depreciation figures used by the vehicle financing industry will continue to be based on MSRP, as required by the automotive finance industry, according to an announcement from ALG.

Edmunds.com hopes to have the figures available on their Web site within the next two weeks, a spokesperson for Edmunds.com said.