Quick Answer
Systematic (market) risk hits the whole market and cannot be diversified away; it is measured by beta. Unsystematic (company-specific) risk is unique to one issuer or industry and can be reduced or eliminated through diversification. Correlation between holdings determines how much diversification benefit a portfolio actually gets.
With your understanding of diversification and portfolio construction in place, you can now dig into the two fundamental categories of investment risk. This distinction is the foundation for everything that follows: beta, alpha, and CAPM all build on it.
What Is Systematic (Market) Risk?
- Systematic risk affects the entire market or a broad segment of the market
- Cannot be eliminated through diversification; it is non-diversifiable
- Examples: interest rate changes, inflation, reinvestment risk, market declines, currency fluctuations, political events, war
- Can only be mitigated through hedging (options, inverse ETFs) or asset allocation across uncorrelated asset classes
- Measured by beta (covered in the next section)
Memory Aid: PRIME lists the five systematic risks:
- Purchasing power risk (inflation)
- Reinvestment risk
- Interest rate risk
- Market risk
- Exchange rate risk
Key point: When the entire market declines, nearly all stocks decline with it regardless of how diversified the portfolio is. That is systematic risk in action.
What Is Unsystematic (Company-Specific) Risk?
- Unsystematic risk is unique to a specific company or industry
- CAN be reduced or eliminated through diversification
- Also called diversifiable risk, specific risk, or idiosyncratic risk
- Examples: management changes, product recalls, labor strikes, lawsuits, regulatory actions affecting one industry
What Are the Subtypes of Unsystematic Risk?
| Subtype | Description |
|---|---|
| Business risk | Risk inherent in the company's operations and competitive environment |
| Financial risk | Risk from the company's use of debt (leverage); higher debt = higher financial risk |
| Liquidity risk (security-specific) | Risk that a thinly traded security cannot be sold quickly at a fair price |
Exam Tip: Gotchas
- Diversification eliminates unsystematic risk, NOT systematic risk. The risk that can be eliminated through diversification is always unsystematic/diversifiable/company-specific risk, never systematic/market risk.
How Do Systematic and Unsystematic Risk Compare at a Glance?
| Feature | Systematic Risk | Unsystematic Risk |
|---|---|---|
| Also called | Market risk, non-diversifiable risk | Company-specific risk, diversifiable risk |
| Scope | Entire market | Single company or industry |
| Examples | Inflation, interest rates, recession, war | Management fraud, product recall, labor strike |
| Diversification | Cannot eliminate | Can eliminate |
| Measured by | Beta | Not measured by a single standard metric |
| Mitigation | Hedging, asset allocation | Diversification |
Exam Tip: Gotchas
- Asset allocation and diversification are not the same tool, even though this table lists them side by side. Diversification means holding many different securities or issuers so no single company's failure sinks the portfolio; it cancels out company-specific (unsystematic) risk through low correlation among individual holdings.
- Asset allocation means setting the mix of broad asset classes (stocks, bonds, cash, alternatives). It manages exposure to market-wide (systematic) risk, since different asset classes respond differently to the same economic forces. A portfolio holding 200 different stocks is highly diversified but still carries full stock-market systematic risk; shifting some of that money into bonds or cash is what actually reduces that exposure.
How Does Correlation Affect Diversification?
The effectiveness of diversification depends on how portfolio holdings move relative to each other. This relationship is measured by the correlation coefficient, which ranges from -1.0 to +1.0.
Think of it this way: If two investments always move in lockstep (correlation of +1.0), owning both is no different from owning one. The more they move independently or in opposite directions, the more one can cushion losses in the other.
| Correlation Coefficient | Meaning | Diversification Benefit |
|---|---|---|
| +1.0 | Perfectly positively correlated (move in the same direction, same magnitude) | No diversification benefit |
| 0 | No correlation (movements are unrelated) | Moderate diversification benefit |
| -1.0 | Perfectly negatively correlated (move in opposite directions, same magnitude) | Maximum diversification benefit (risk can theoretically be eliminated) |
Key principles:
- In practice, most securities have positive correlations between 0 and +1.0
- Diversification benefits begin as soon as correlation is less than +1.0
- The lower the correlation between holdings, the greater the reduction in overall portfolio risk
- Adding an asset with a negative correlation to an existing portfolio can significantly reduce portfolio volatility
Exam Tip: Gotchas
- Two stocks in the same industry tend to have high positive correlation. Adding a second oil stock to a portfolio that already holds one provides very little diversification benefit. To judge whether adding a particular security improves diversification, look at the correlation or sector. Low correlation = better diversification.
What Should You Check on Exam Day?
- Systematic risk cannot be diversified away; it is mitigated only by hedging or asset allocation across uncorrelated asset classes.
- Unsystematic risk is the risk diversification actually removes; know its subtypes: business, financial, and security-specific liquidity risk.
- Beta measures systematic risk only; standard deviation measures total risk.
- Correlation of +1.0 gives no diversification benefit; -1.0 gives the maximum possible benefit. Benefit begins as soon as correlation drops below +1.0.
- Remember PRIME for the five systematic risks: purchasing power, reinvestment, interest rate, market, and exchange rate.