In the 1970s, during the rise of the women’s movement, one popular T-shirt proclaimed: “I haven’t come a long way, and I’m not a baby.” It was a clever riposte to a high-profile cigarette ad campaign of the era that linked smoking and feminism.

That T-shirt slogan is one that female lawyers at large firms today might want to adopt as their own. Years after the last of those shirts wore out in the laundry, the mean proportion of women at large firms has remained close to about one-third. And while the ranks of female partners have grown steadily, women still account, on average, for fewer than one in five big-firm partners. The greatest numbers of female lawyers remain concentrated at the associate level.