Diversification
Diversification is spreading money across assets that do not all move together, so that a loss in one holding has a smaller effect on the whole portfolio.
Diversification is the closest thing in finance to a free lunch: combining assets that do not move together can reduce the swings of a portfolio without reducing its expected return. For traders it also means spreading risk across setups, markets and time, so that one bad trade or one bad sector cannot do serious damage. This entry explains how diversification works, where it fails, and how traders apply it beyond simply owning many things.
- Category
- Risk Management
- Reading time
- 4 min
- Also called
- Diversify, Diversified portfolio, Spreading risk
- Updated
Diversification in plain words
If all your money is in one stock, one bad news story can cost you a lot.1 Spread it across many unrelated holdings, and a single disaster becomes a small dent.
The key word is unrelated. Ten stocks in the same industry are not diversified; they tend to move together. What matters is low Correlation.
How to diversify, step by step
Spread across assets
Different companies, sectors and asset classes.2
Check correlation
Prefer combinations that do not all move together. See Correlation.
Limit any single position
Cap the size of each holding. See Position Sizing.
For traders: diversify setups
Different strategies and markets smooth results. See Trading Strategy.
Cap correlated risk
Limit total risk in any one theme. See Risk Stacking.
Rebalance
Bring weights back to targets periodically. See Rebalancing.
Worked examples
Example 1 — One stock vs. twenty
SpreadAn investor has $20,000. One holding falls 50% after bad news.
| All in that stock | −$10,000 (−50%) |
| Spread over 20 stocks ($1,000 each) | −$500 (−2.5%) |
Diversification turns a disaster into a dent.
Example 2 — Fake diversification
ConcentratedA trader holds eight positions, all in large US technology stocks, correlated around 0.85. The sector drops 12%.
| Portfolio drop | ≈ 12% |
Eight positions, one bet. Real diversification needs assets that behave differently.
Example 3 — Diversifying strategies
StrategiesA trader runs a trend-following system and a mean-reversion system. In a sideways year the trend system loses −6% and the mean-reversion system gains +9%.
| Combined (equal capital) | +1.5% |
Strategies that do well in different market conditions can smooth overall results. See Trend Following and Mean Reversion.
Ways to diversify
| Aspect | Reduces | Limitation |
|---|---|---|
| Many stocks | Company-specific risk | Not market-wide risk |
| Different asset classes | Dependence on one market | Correlations can rise in crises |
| Different strategies | Dependence on one market regime | More complexity |
| Time (spreading entries) | Timing risk | Slower deployment. See Dollar-Cost Averaging |
Why diversification matters
Avoiding single-point failures
No one company or trade can ruin the account. See Concentration Risk.
Smoother returns
Lower volatility for the same expected return.
Survival
Smaller drawdowns keep you in the game. See Drawdown.
Behaviour
Smoother results make it easier to stick to a plan.
Advantages and disadvantages
Advantages
- Reduces company-specific and position-specific risk.
- Can lower volatility without lowering expected return.
- Protects against single unexpected events.
Disadvantages
- Cannot remove market-wide risk.
- Correlations tend to rise in crashes.
- Too many positions dilute good ideas and are hard to manage.
- Adds costs and complexity.
Going deeper
Read as far as you need. Each level builds on the one before it.
Diversifiable vs. market risk
Beginner
Company-specific risk shrinks as you add unrelated holdings. Market-wide risk — a broad sell-off — stays, no matter how many stocks you own.
Diminishing returns
Intermediate
Each additional unrelated holding reduces risk by less than the one before. Beyond a few dozen stocks, adding more changes little, while making the portfolio harder to follow.
Diversification and leverage
Advanced
Lower volatility from diversification is what allows some funds to use leverage. If correlations rise unexpectedly, that combination can produce large losses. See Leverage and Risk Parity, Minimum Variance and the Efficient Frontier.
Common mistakes
Owning many similar assets
Count correlations, not tickers.
Over-diversifying
Too many small positions dilute returns and attention.
Forgetting crisis behaviour
Test how holdings behaved in past sell-offs.
Never rebalancing
Winners grow until the portfolio is concentrated again.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Diversify across assets that do not move together.
- Correlation, not the number of positions, determines the benefit.
- It removes company-specific risk, not market-wide risk.
- Correlations rise in crises, so expect less protection then.
- Traders can diversify across setups, markets and strategies too.
Frequently asked questions
How many stocks do I need to be diversified?
Can you be too diversified?
Does diversification help in a crash?
Further learning
- Correlation
The measure that makes diversification work.
- Hedging
A more targeted way to reduce risk.
- Position Sizing
Capping any single position.
- Drawdown
What diversification helps limit.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- Investor.gov (SEC). Diversification (glossary) (opens in a new tab) Checked .
- Investor.gov (SEC). Asset Allocation (glossary) (opens in a new tab) Checked .
Read more elsewhere
- Trading Metrics (our sister site): Diversification Ratio (opens in a new tab)
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. Trading Metrics is our sister site, under the same ownership; we are not affiliated with any other publisher linked above. Last reviewed . Report an error or request a source credit.