Much research has argued the business case for gender diversity on boards. But it is pressure applied by big shareholders that seems to have progressed the cause of women in US boardrooms. New research shows that campaigns by the "Big Three" shareholders—BlackRock, State Street and Vanguard—over three years appears to have significantly shifted the composition of US boards in favour of women. The news comes in the same week Nasdaq, the tech market, sought permission from US regulators to introduce new listing rules that would compel listed companies to disclose diversity statistics for their boards. While a rule change would mark