(WIRED) -- In an effort to streamline and simplify the maturity ratings of software in mobile app stores, CTIA, the international wireless industry association, yesterday proposed a ratings system that store owners could voluntarily adopt. Google and Apple basically told the CTIA to stuff it -- they're sticking with their own rating schemes. "We've put a lot of effort into Android Market's rating system, which now works well globally," Google spokesman Christopher Katsaros said in a statement. "While we support other systems, we think it's best for Android users and developers to stick with Android's existing ratings." Apple, too, has outlined its app review guidelines in extensive detail, but has not publicly commented on the CTIA app rating issue.