[T]he demands for greater board diversity continue, raising the question of whether external pressure from shareholders, media, and advocacy groups actually causes firms to appoint women to their boards. The answer is yes, a new study concludes, but there’s a catch: Firms under pressure to appoint female directors tend to do so by adding board seats, the authors found, rather than by replacing a male director. And these women are much less likely to serve on major committees after they’re appointed than men.