Experts and observers have long argued that there is a benefit to firms of having more women in senior decision-making roles. The reasons are many, including the importance of diversity, the fact that senior women more readily represent female customers (the majority of buyers in many industries), and a general openness to talent. Some new research done at Columbia finds that companies with women in the top team do enjoy a performance benefit. Interestingly, this doesn't apply to firms that have a female CEO (rare though they are). Worth a look.