A video game content rating system is a system used for the classification of video games into suitability-related groups. Most of these systems are associated with and/or sponsored by a government, and are sometimes part of the local motion picture rating system. The utility of such ratings has been called into question by studies that publish findings such as 90% of teenagers claim that their parents "never" check the ratings before allowing them to rent or buy video games, and as such calls have been made to "fix" the existing rating systems. Video game content rating systems can be used as the basis for laws that cover the sales of video games to minors, such as in Australia. Rating checking and approval is part of the game localization when they are being prepared for their distribution in other countries or locales. These rating systems have also been used to voluntarily restrict sales of certain video games by stores, such as the German retailer Galeria Kaufhof's removal of all video games rated 18+ by the USK following the Winnenden school shooting.