Corporate governance has undergone a profound transformation in the last two decades, as a result of the legislative and regulatory changes that have expanded director responsibilities as well as the rise of more vocal shareholders. Yet the composition of the board of directors has not changed as rapidly as other governance practices, and to this day many public company boards do not see any turnover that is not the result of retirement at the end of a fairly long tenure.

According to a comprehensive review of SEC filings made in 2018, 50.4 percent of Russell 3000 companies and 42.5 percent of S&P 500 companies disclosed no change whatsoever in the composition of their board of directors. More specifically, they neither added a new member nor replaced an existing one. In those cases where a replacement or addition did happen, it rarely affected more than one board seat; and only one-quarter of boards elected a first-time director who had never served on a public company board before.

Source: Corporate Board Practices in the Russell 3000 and S&P 500: 2019 Edition | The Conference Board