Portfolio design
Common DIY portfolio mistakes: overlapping funds, accidental US tech concentration, oversized winners, pie imbalance, no broad core and unmanaged fee drag.
What the holdings really say
A DIY portfolio can look diversified because it has lots of lines on the screen. Underneath, it may still depend on the same few companies, markets or themes.
The useful question is not how many holdings you own. It is how many different risks you actually have.
Owning twenty holdings is not diversification if they all hold Apple, Microsoft and Nvidia underneath. Diversification is about the risks you own, not the number of line items on the screen.
The better question is: how many genuinely different bets do I have? The answer is often smaller than the account page suggests.
A global tracker is already heavily weighted to the United States, and its largest positions are a few mega-cap technology companies. Add an S&P 500 fund and a Nasdaq fund “for growth” on top, and you have tripled down on the same dozen names while believing you spread out.
There is nothing wrong with liking US tech. There is plenty wrong with betting most of your future on it by accident.
Concentration rarely arrives by decision. A holding does well, grows into a large slice of the portfolio, and now its swings drive your whole result, even though you never chose that weight. The position chose it for you.
Refusing to trim a winner is a real decision with real risk, even though it never feels like one. A target weight turns drift into a choice.
Splitting an account into neatly labelled pies feels organised and looks diversified. But if one pie quietly holds most of the money, the labels are describing a balance the weights do not have. Organisation is not the same as diversification.
The fix is unglamorous: set a target weight per pie and steer new money toward the underweight ones, instead of topping up whatever already dominates.
A portfolio made mostly of single stocks and thematic funds without a broad, low-cost core is a bet that you will keep picking winners. That is a hard game to play for decades.
A boring core can carry the long-term allocation while conviction picks sit on top as a deliberate, sized layer. The problem is when the story stocks become the whole plan.
A high-volatility, all-equity portfolio with no bonds, cash or defensive holdings can fall hard, and the real damage is behavioural. If a drawdown forces you to sell to raise cash, or simply frightens you out at the bottom, a paper loss becomes a permanent one.
You do not need a large defensive sleeve. You need it to have a defined job before the day you are tempted to capitulate.
You can get the allocation right and still hand a chunk of the result to fees, FX churn and avoidable tax. These are not glamorous, which is exactly why they get ignored and why they keep quietly winning.
Allocation decides the shape of your returns. Costs and tax decide how much of them you keep.
When concentration is deliberate
A concentrated portfolio is not automatically wrong. Some investors knowingly choose a US-heavy, equity-heavy or single-stock-heavy allocation. The problem is being concentrated by accident while believing you are diversified.
Use in DiviScout
DiviScout's Portfolio Doctor scans an imported portfolio for concentration, fund overlap, missing broad core, defensive ballast, pie balance and fee drag, then summarises what stands out. It is name-based and uses no live prices. Treat it as a prompt to review your own decisions, not financial advice.
Because diversification depends on the underlying exposures, not the number of funds. If several funds hold the same mega-cap companies, they move together and behave like one concentrated position with extra admin.
Check the index each fund tracks. A global fund already holds large US companies, so adding an S&P 500 or Nasdaq fund stacks more weight on the same names rather than diversifying.
Not on its own. If one pie holds most of the money, the account is still concentrated. Diversification is about the underlying weights, not how many buckets you create.
No. A concentrated portfolio chosen deliberately is a strategy. The mistake is being concentrated by accident while believing you are diversified, because then the risk is one you never agreed to take.
No. It runs rule-based, name-based checks on your imported data with no live prices and cannot see inside funds. Treat it as a prompt to review your own decisions, not as advice.