Rich Juzwiak looks at how PG-13 has become the rating you want:

It’s simple math, really: Movies rated PG-13 make more money on average ($42 million per picture versus G’s $38.5 million, PG’s $37 million and R’s $15 million). Getting blessed with PG-13 ensures that the odds are ever in your favor. In this economy, who wants to gamble?

To some degree it’s a self-fulfilling prophecy: as studios make most of their blockbusters PG-13, most blockbusters will be PG-13.

While there are always notable exceptions (Safe House is a recent one), in most cases it doesn’t seem worth arguing anymore: if you’re making an expensive movie that could conceivably be less than an R, it probably should be PG-13 — and that comes at the scripting stage.

From personal experience, one of the worst things that can happen to your movie is to cut it down to a safer rating after you’ve shot it. It’s not just losing the F-words. It’s losing the moments that called for the F-words. If when writing the script you knew you could only say it once and in a non-sexual context, you would write scenes in a way that didn’t demand it.

Similarly, an R-rated action scene cut down to PG-13 feels neutered, while an action scene designed for PG-13 can plan for the absence of gore at the outset. People criticize the shaky-cam in The Hunger Games, but it was clearly a choice made from the beginning in order to show the feeling of violence without the bloodshed.

That worked out well for them.