There’s no argument that the MPAA ratings system for movies has wandered far afield of what was intended when it was first introduced in 1968. At the time, most movies were rated G and the whole family went to see them. Now, a G-rated movie is pretty much aimed at young children, and PG is almost there. The rating modern movies want is PG-13, the new rating introduced in 1984, so the lucrative teenage market can get into the theater and know they will see the the maximum adult content allowed for them.
This video from Pitchfork explains how we got to this point. You’ll find a more involved article about the PG-13 rating at The Dissolve. -via Metafilter