Thirty Years of Change: The Evolution of Classified Boards

We combine machine learning with manual inspection to determine the classified board status of over 12,500 firms from 1996 to 2020. We find that while the fraction of S&P 1500 firms with a classified board fell from 58% to 30% over this period, it rose from 40% to 53% for non-S&P 1500 firms. Increasing attention to governance and rising index ownership of S&P 1500 firms appear to drive these trend differences. Our results suggest the conventional wisdom that classified boards are becoming an endangered species is inaccurate for most firms. Rather, they are hiding among firms neglected by commercial databases.