The survey, which also looked at R-rated movies, DVDs and "Parental Advisory"-labeled music, found that video games had the best enforcement rate.
The FTC also broke out its statistics by retailer. GameStop topped the list with a 94 percent enforcement rate, while Hollywood Video came in last with 60 percent enforcement.
The FTC announced its results just as Republican representative Lee Terry and Democratic representative Jim Matheson introduced a bill in the U.S. House of Representatives that seeks to reinforce Entertainment Software Ratings Board ratings at retail with $5000 fines for violators.
According to the FTC's study, ratings enforcement at retail has increased steadily since 2000, when 80% of its undercover shoppers successfully purchased M-rated games.
The ESRB conducts its own secret-shopper studies using the same surveyors as the FTC. Its most recent survey in November 2007 found 76 percent compliance with store policies.
"Video game retailers have clearly stepped up their efforts to enforce their store policies, and they deserve recognition for these outstanding results," said ESRB president Patricia Vance, in a statement released today. "We commend and applaud retailers for their strong support of the ESRB ratings, and will continue working with them to help ensure that these levels of compliance are sustained if not further increased."
Undercover Shoppers Find it's Increasingly Difficult for Children to Buy M-Rated Games [Federal Trade Commission