Signorielli, N. (2005). Age-based ratings, content designations, and television content: Is there a problem?. Mass Communication and Society, 8(4), 277-298. Retrieved July 16, 2009, doi:10.1207/s15327825mcs0804_1

An analysis of 9 week-long samples of prime-time network programming broadcast between the fall of 1997 and the fall of 2003 found that more than 8 out of 10 programs were labeled with an age-based rating (TV-G, TV-PG, TV-14, or TV-MA), whereas fewer than 4 in 10 programs were also labeled with content-based ratings (V, S, L, or D). Although programs with age- and content-based ratings accurately reflected sexual and violent content, a sizable number of programs without content-based ratings also had sexual and violent content. Ratings provide parents with incomplete information on which to base viewing decisions. (PsycINFO Database Record (c) 2008 APA, all rights reserved)(from the journal abstract)