Lesson 3 of 7 · All lessons in this module
  1. The risk-free asset, the market portfolio and the CMLVideo lesson
  2. Lending, borrowing and leveraged portfolios on the CMLVideo lesson
  3. Systematic and nonsystematic riskVideo lesson
  4. Return-generating models, the market model and betaVideo lesson
  5. The CAPM: assumptions, the SML and its limitsVideo lesson
  6. Sharpe ratio, Treynor ratio, M² and Jensen's alphaVideo lesson
  7. Applying the CAPM: budgeting, security selection and portfolio buildingVideo lesson

Lesson 3 of 7 · 12 min

Systematic and nonsystematic risk

Total risk splits into market-wide risk that nobody can diversify away and company-specific risk that diversification removes, so only the market-wide part earns a reward.

In short

  • Systematic risk (market, non-diversifiable risk) comes from economy-wide factors: interest rates, inflation, business cycles, political uncertainty, widespread disasters.
  • Nonsystematic risk (company-specific, industry-specific, diversifiable, idiosyncratic risk) comes from local events such as a failed product trial or a factory accident.
  • Total variance = systematic variance + nonsystematic variance. The sum works for variances, not for standard deviations.
  • If diversifiable risk were rewarded, everyone would buy it and diversify it away for free; demand would push its reward to zero. Only systematic risk is priced.
  • A risk-free asset has neither kind of risk; the market portfolio has only systematic risk. Risk-averse investors should hold well-diversified portfolios.

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