How to spot concentration
- Any single stock above roughly 5–10% of the total.
- One sector making up a large share, such as technology.
- All holdings tied to one country or currency.
- Several funds that own the same top companies.
Hidden concentration
Even broad index funds can be concentrated. Market-cap weighted indexes give the largest companies the biggest weights, so a small group of firms can drive a large share of the index's movement.
Example
If 40% of a $100,000 portfolio sits in one stock and that stock falls 50%, the portfolio loses $20,000 from that position alone. Spread across 25 stocks at 4% each, the same single-stock drop costs $2,000.
Why people end up concentrated
Employer stock plans, a big winner that grew to dominate, or strong conviction in one theme. None of these are necessarily wrong, but it helps to make the choice deliberately.
Key takeaways
- Concentration means a lot riding on a few things.
- It raises both potential gains and potential losses.
- Check fund overlap and index weights for hidden concentration.