Position sizing protects you from any single trade. Portfolio construction protects you from the more dangerous problem: several positions that appear independent but are quietly the same bet.
Correlation, the hidden concentration
This is the most common form of accidental concentration among Indian retail investors, and it usually happens through enthusiasm rather than carelessness: you research a sector, develop a view, and then buy the four names you liked best within it.
- Cap exposure to any single sector at roughly 20–25% of the portfolio.
- Remember that market-cap tiers correlate too — a portfolio of twelve smallcaps is one bet on smallcap sentiment.
- In genuine market-wide crashes, correlations converge towards one. Diversification helps against company-specific risk, not against systemic risk.
- The only real protection against systemic risk is asset allocation — how much you hold in equity at all.
How many stocks?
| Number of stocks | Effect | Suits |
|---|---|---|
| 1 – 3 | Extreme outcomes in both directions. One bad call is catastrophic. | Almost nobody |
| 5 – 8 | Concentrated. Requires deep conviction and real research on each. | Experienced investors with genuine information advantage |
| 12 – 20 | Most company-specific risk diversified away while each holding still matters | The practical sweet spot for most serious investors |
| 30 – 50 | Approaching index-like behaviour, with much more work and cost | Rarely justified — consider an index fund instead |
| 50+ | You have built an expensive index fund by hand | Nobody |
Concentration versus diversification, honestly
- Your best ideas are, by definition, better than your tenth-best.
- You can actually follow each business properly.
- Large returns require positions large enough to matter.
- Buffett, Munger and most great investors ran concentrated books.
- You are far less certain than you feel about any single company.
- Fraud and sudden regulatory change cannot be modelled.
- One 90% loss in a 5-stock portfolio is close to unrecoverable.
- The great concentrated investors also had information and access you do not.
The honest resolution: concentration is the correct choice only if your research genuinely gives you an edge on each name, and if you can psychologically tolerate large drawdowns without abandoning the strategy. Most people substantially overestimate both. Twelve to twenty positions is the sensible default, and moving away from it should require an argument.
Rebalancing
Winners grow to dominate a portfolio. A position that started at 8% and becomes 30% is now a concentration risk you never consciously chose. Rebalancing trims it back — but it also cuts your winners, which is exactly what you should usually avoid.
Asset allocation comes first
Before any of this, one decision dominates everything: what fraction of your total savings is in equity at all. In a 40% market decline, someone 100% in equity loses 40% of their net worth and someone 50% in equity loses 20%. No amount of stock selection compensates for getting that split wrong relative to your temperament and your timeline.
Your portfolio: 22% HDFC Bank, 18% ICICI Bank, 15% SBI, 14% Bajaj Finance, 12% Kotak, and 19% across three IT stocks. How diversified are you?
Purani baat hai par log phir bhi karte hain. Aur nayi galti yeh hai ki 8 alag stock le liye — par sab ek hi sector ke. Woh 8 tokri nahi, ek hi tokri ke 8 khaane hain. Tokri girne pe sab toot-te hain. Diversification ginti se nahi, alag-alag wajah se hota hai.
- Five banks is one bet, not five positions. Correlation is hidden concentration.
- Twelve to twenty holdings captures most of the diversification benefit available.
- Cap any single sector at roughly 20–25% of the portfolio.
- Rebalance when position size threatens survival, not merely because something went up.
- Asset allocation — how much equity at all — matters more than which stocks.
Mark it done to track your progress through the curriculum.
Common questions
Short, direct answers to what people ask about this topic.
- how many stocks should a portfolio hold
- The statistical benefit of spreading risk falls off sharply after roughly fifteen genuinely uncorrelated holdings, and around twelve to twenty is where most company-specific risk is diversified away while each position still matters to the result. Beyond about thirty you are approaching index-like behaviour with far more work and cost. This is education, not a recommendation for your situation.
- correlation meaning in a stock portfolio
- Correlation measures how much two holdings tend to move together, and it is what decides whether diversification is real or only apparent. Five private banks bought separately are effectively one bet, and a portfolio of twelve smallcaps is one bet on smallcap sentiment — different names, the same underlying exposure.
- selling part of what has risen and buying what has lagged to restore target weights is called
- Rebalancing. It returns a portfolio to the allocation you chose after price moves have drifted it away, without needing any forecast. The care needed is that it also trims winners, so the more defensible trigger is risk — cutting a position back when its size threatens your ability to survive being wrong about it, rather than simply because it went up.
- why does asset allocation matter more than stock picking
- Because the split of your total savings between equity, debt, cash and everything else decides how much of your net worth a market fall can reach at all. In a 40% equity decline, someone entirely in equity loses 40% of their net worth while someone half in equity loses 20% — a gap no amount of stock selection makes up for.
- difference between concentration and diversification
- Concentration means holding few positions, so being right pays a great deal and being wrong hurts a great deal; diversification spreads across many, so no single mistake is fatal and no single winner transforms the result. Neither is automatically correct, and diversification only works if the holdings are genuinely independent rather than the same bet under different names.