An FTC undercover shopper study found that only 20 percent of underage teenage shoppers were able to buy M-rated videogames.

The FTC called the results a "major improvement" from other undercover shopper surveys. 2006, for instance, found that 42 percent of undercover shoppers were able to buy mature games.

Entertainment Software Rating Board boss Patricia Vance said in a statement, "Videogame retailers have clearly stepped up their efforts to enforce their store policies, and they deserve recognition for these outstanding results."

But retailers in other entertainment sectors weren"t as diligent in enforcing entertainment ratings. About half of the undercover shoppers were able to buy R-rated, unrated and "Parental Advisory"-labeled DVDs and music.

Movie theaters sold R-rated movie tickets to unaccompanied children about 35 percent of the time.

Top game retail chain GameStop turned away underage consumers 94 percent of the time, the best of all game retailers, specialist or big-box. Hollywood Video was the worst when it came to selling M-rated games to minors, with 40 percent able to buy mature games from stores.

More details on the FTC"s findings can be found here.