Glossary term
Unsystematic Risk
Idiosyncratic risk specific to a single company, industry or position — fraud, a lost contract, a failed product launch, a regulatory strike. Diversifiable: adding uncorrelated names reduces unsystematic risk toward zero. Systematic (market) risk cannot be diversified away. Closelook's Reference Portfolios diversify unsystematic risk while preserving thematic systematic exposure.
Definition & Context
In Modern Portfolio Theory, total risk decomposes into systematic risk (market-wide factors: rates, recession, liquidity) and unsystematic risk (specific to one company or industry). The CAPM result is that only systematic risk commands a risk premium because unsystematic risk can be diversified away at near-zero cost. Empirically, the marginal benefit of diversification diminishes quickly: 20 uncorrelated names reduces 80% of unsystematic variance; 50 names gets you to 95%.
Unsystematic risk is underrated by most investors because each idiosyncratic event looks unlikely ex-ante. Fraud at Wirecard, Enron, Theranos. A failed phase-3 trial. A surprise FTC suit. A new competitor eating lunch. These events are low-probability individually and certainty in aggregate over a 20-year holding period. Position-size discipline — never exceeding 5% in a single name outside a conviction portfolio — is the practical answer.
Why It Matters for Investors
Closelook’s Reference Portfolios are built to diversify unsystematic risk while keeping thematic systematic exposure (AI infrastructure in Rubin, European AI sovereignty in Euro-AI, agentic winners in AW25). Global Tech 50 holds 50 names precisely to get most of the unsystematic-risk benefit without diluting thematic signal. Hypergrowth, by contrast, runs 18 names and accepts elevated unsystematic risk as the cost of concentrated upside.
Related Concepts
Unsystematic risk is measured in part via Maximum Drawdown, managed through Kelly Criterion position sizing, and contributes to the denominator of the Sharpe Ratio.