Diversification: Don’t Put All Your Eggs in One Basket
The only free lunch in investing
What Is Diversification?
Diversification means spreading your money across different types of investments so that a bad performance in one doesn’t wipe you out. If you own shares in 1 company and it goes bust, you lose everything. If you own shares in 1,000 companies, one going bust barely registers.
Key Concept
Nobel laureate Harry Markowitz called diversification “the only free lunch in finance.” You can reduce risk without necessarily reducing expected returns — simply by not putting everything in one place.
Asset Classes
| Asset Class | Risk | Return | Role in Portfolio |
|---|---|---|---|
| Cash | Very low | 1–5% | Emergency fund, stability |
| Bonds | Low–medium | 3–5% | Income, dampens volatility |
| Property | Medium | 5–8% | Income, inflation hedge |
| Equities | Medium–high | 7–10% | Long-term growth engine |
| Commodities | High | Variable | Inflation hedge, diversifier |
Geographic Diversification
The UK represents only about 4% of the global stock market. If you only invest in UK companies, you’re ignoring 96% of the world’s opportunities. A global index fund gives you exposure to:
- US (~60% of global markets) — tech giants, innovation
- Europe (~15%) — healthcare, industrials, luxury
- Japan (~6%) — manufacturing, technology
- Emerging markets (~10%) — high growth potential (China, India, Brazil)
- UK (~4%) — dividends, banking, energy
Sector Diversification
Different sectors perform well at different times. Technology boomed in 2020–21 but crashed in 2022. Energy crashed in 2020 but soared in 2022. Owning both smooths out the ride.
The Efficient Frontier (Simply Explained)
Real-World Example
Imagine plotting every possible combination of shares and bonds on a graph (risk on one axis, return on the other). Some combinations give you the most return for a given level of risk. The line connecting these optimal points is the “efficient frontier.” In practice, it means there’s a sweet spot of shares-to-bonds that maximises returns for your risk tolerance.
Model Portfolios by Age / Risk Tolerance
| Profile | Equities | Bonds | Cash | Typical Age |
|---|---|---|---|---|
| Aggressive | 90% | 10% | 0% | 20s–30s |
| Growth | 75% | 20% | 5% | 30s–40s |
| Balanced | 60% | 30% | 10% | 40s–50s |
| Conservative | 40% | 40% | 20% | 50s–60s |
| Income | 20% | 50% | 30% | Retired |
Rebalancing
Over time, your allocation drifts. If shares do well, they become a larger proportion of your portfolio, increasing your risk. Rebalancing means periodically selling some winners and buying more of the underperformers to get back to your target allocation. Do it once or twice a year — don’t obsess over it.
Warning
Diversification does not eliminate risk entirely. In a true market crash (like 2008 or March 2020), almost everything falls at once. Diversification protects you from individual failures, not market-wide panic. That’s why you also need an emergency fund in cash.