Fund-management skill is becoming rather like the 19th-century concept of a “God of the gaps”. Once humans attributed the weather or earthquakes to divine intervention; then they discovered high-pressure systems and plate tectonics. The number of events that required a heavenly explanation (the gaps) grew ever smaller.

Skill, or alpha, is fast becoming a residual: the explanation that remains when all other factors have been discounted. That is not yet a crisis for the industry, mainly because it is still so hard for clients to distinguish skill from luck. But for any thoughtful fund-management executive, it ought to be a long-term worry.