Whether active management adds value, or whether investors get a better deal from cheaper passive funds, has been much debated in recent years. One thing that's not so often raised, however, is whether passive managers can ever do as good a job of holding companies to account.

Instead, the debate has almost solely focused on whether, and why, active managers can consistently outperform passive. That's understandable, but the lack of focus on passive shareholders' engagement with companies is a shame.