A new study by the Center For the Study of Women in Television in Film concludes that there are more female characters on TV than ever, and that female characters are evenly split between workplace shows and domestic shows, whereas in the past, the majority of TV women were playing The Wife or The Daughter. Not to overstate the significance of that, because a likely reason is just that workplace shows now outnumber domestic shows (particuarly with the collapse of the domestic comedy).
Also, statistics can lie, and so can categorization. I’m assuming that most of the women on 30 Rock fit into the category of characters who are “not defined by their marital status,” because they have jobs and aren’t married. But let’s face it, the three most prominent characters on 30 Rock are a neurotic single woman who can’t land a man and has been explicitly compared to the comic-strip character Cathy (Liz Lemon); an airheaded idiot who wants a rich husband (Jenna) and a ditzy, lazy sexpot (Cerie). Nothing wrong with that, since all the guys are stereotypes too; I’m just using that as an example of why these studies are of limited utility. Still, it’s pretty clear that networks are making more of a play for female viewers now, and including more female characters who have some kind of existence on their own as opposed to being the Hero’s Girl.