Meanwhile, life moved forward. Their salary increased, they bought property in Dubai, their employer awarded company shares and their savings grew. A mortgage appeared, followed by school fees. On paper, everything might look impressively diversified. Look underneath, however, and a different picture may emerge. The global fund, US equity fund, technology ETF and AI fund could all own many of the same companies. The investor believes they are adding something new, when they may simply be increasing exposure to what they already own.

Concentration often develops this way: gradually, through investments that have done well. Something rises in value, so we hold on to it. It rises further, so we buy more.

Eventually, what began as a sensible…