Portfolio Construction
Why Diversification Isn't Just About Asset Classes
A portfolio can hold twenty different funds and still be far less diversified than it looks on paper.
The mistake
Counting the number of holdings is not the same as measuring how independently those holdings actually behave from one another.
What diversification is actually for
Diversification exists to reduce the impact of any single risk on the whole portfolio. It works when the assets held genuinely respond differently to the same event. It fails - quietly, and usually at the worst possible time - when assets that look different on a fact sheet turn out to move together under pressure.
Where hidden correlation hides
Geographic concentration
A portfolio split across ten different JSE-listed shares is still one bet on the South African economy, the rand, and local policy risk - however different the individual companies appear.
Sector overlap
Property, financials, and retail shares often move together in a downturn because they share the same underlying sensitivity to interest rates and consumer spending, regardless of how the portfolio is labelled.
Currency exposure
Offshore diversification can quietly reintroduce concentration through the rand - if every offshore holding is unhedged, the portfolio's fortunes are still tied to a single currency view.
Manager style drift
Several unit trusts with different names and fact sheets can hold strikingly similar underlying positions if their managers follow the same investment style or benchmark.
The dimensions that matter beyond asset class
Asset class
Equities, bonds, property, and cash behave differently across a cycle - the traditional and still-necessary starting point.
Geography
Local and offshore exposure reduces reliance on any single economy, currency, or regulatory environment.
Time horizon
Matching each pool of capital to when it is actually needed prevents short-term market noise from forcing long-term decisions.
Manager and style
Blending different investment philosophies - value, growth, quality - reduces the risk of any single approach underperforming for an extended period.
Liquidity
Holding a mix of liquid and less liquid assets ensures a market downturn never forces a sale at the worst possible time to raise cash.
A useful test
A simple way to stress-test a portfolio is to ask: in a sharp, broad market decline, which of these holdings would I expect to hold up, and why? If the honest answer is “most of them would fall together,” the portfolio is concentrated, regardless of how many line items appear on the statement.
Conclusion
Genuine diversification is a discipline, not a headcount. It requires looking past fund names and fact sheets to understand what actually drives returns in each holding - and deliberately choosing exposures that do not all rely on the same story to succeed.
Reviewing how your specific holdings correlate under stress is a worthwhile exercise most portfolios never get - and one worth doing before the next downturn, not during it.
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