The 1980s saw the continued rise of the blockbuster, an increased amount of nudity in film and the increasing emphasis in the American industry on film franchises, especially in the science fiction, horror, and action genres. Much of the reliance on these effect-driven blockbusters was due in part to the Star Wars films at the advent of this decade and the new cinematic effects it helped to pioneer. The teen comedy sub-genre saw its popularity rise during this decade. In the US, the PG-13 rating was introduced in 1984, to accommodate films that straddled the line between PG and R.