More progress has been made improving the governance of US corporations during the past couple of years than in the several decades preceding them. New reporting requirements that stock exchanges have ordered in response to high-profile scandals, together with tougher auditing standards under the landmark Sarbanes-Oxley Act, have pushed boards and managers to become far more diligent in preparing and reporting accurate financial information. Boards have also grown acutely aware of their responsibility to shareholders and of the consequences of failing to live up to it, so many have become more independent from management.

But our latest research on board governance in the United States indicates that directors and investors alike feel that, so far, reform has led to only modest improvement. Much more must change, they think, before high-quality board governance can be achieved.

Although the reforms so far have created more work for finance departments, as well as higher accounting expenses, the direct impact on executives and directors hasn’t been particularly troublesome. But the reforms now being demanded by investors and activist advisory groups will be much more of a burden. The investors and directors we surveyed want companies to move toward separating the roles of CEO...