Simon Evan-Cook: Is diversification dead?

Diversification has taken quite a drubbing in recent years. This is coming from a Spurs fan, so you can rest assured I know a drubbing when I see one. That said, although it has not been a fantastic decade for diversification, it is the last two years that have been particularly stark. In a nutshell, holding anything other than America's largest companies or, in the bond world, the longest-duration, US-dollar denominated bonds, has been a largely pointless exercise since 2018. So it is fair to ask then, is diversification itself a waste of time? And a potentially expensive one at that...