oh, and ps, the rating system in the us is a subjective mess that is anything but simple and clear.  that's a great analogy because there's a lot of politics and complaints and personal issues involved, as well as the specific judgment of a small group of people. 

for example, splash was pg, even though daryl hannah is seen "nude" from the back.  so those raters didn't count a bare bottom with no indication of clothes as nudity, i guess.  and i believe there are several occasions where her hair is the only thing separating the movie from an R rating.