What is an Equal Risk Contribution portfolio, and how does the allocation methodology differ from equal weighting or minimum variance?

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AcadiFi · Accepted Answer

An Equal Risk Contribution (ERC) portfolio allocates weights so that every asset contributes the same amount of risk to the total portfolio variance. This is distinct from both equal weighting (which equalizes dollar exposure) and minimum variance (which minimizes total risk regardless of risk distribution). **Conceptual Foundation** Each asset's risk contribution is the product of its weight and its marginal contribution to portfolio risk (MCTR). The ERC condition requires that w_i x MCTR_i is identical for all assets. **Worked Example — Broadhaven Equity Allocation:** Broadhaven manages a four-sector equity portfolio. Here is the comparison across methodologies: | Sector | Volatility | Equal Weight | Min Variance | Equal Risk Contribution | |---|---|---|---|---| | Technology | 24% | 25.0% | 10.2% | 16.8% | | Healthcare | 18% | 25.0% | 22.4% | 22.1% | | Utilities | 12% | 25.0% | 38.7% | 30.4% | | Financials | 20% | 25.0% | 28.7% | 30.7% | | **Portfolio Vol** | — | **16.1%** | **11.8%** | **13.2%** | | Methodology | Risk Contribution Distribution | |---|---| | Equal Weight | Tech: 38%, HC: 24%, Util: 14%, Fin: 24% | | Min Variance | Tech: 8%, HC: 18%, Util: 42%, Fin: 32% | | **ERC** | **Tech: 25%, HC: 25%, Util: 25%, Fin: 25%** | \`\`\`mermaid flowchart TD A["Input: Covariance
Matrix"] --> B["Compute Marginal
Contribution to Risk"] B --> C["Optimize: Set
w_i × MCTR_i = constant"] C --> D["ERC Portfolio
Weights"] D --> E["Each Asset = 25%
of Total Risk"] \`\`\` **Key Differences:** 1. **Equal Weight** — ignores risk entirely; high-volatility assets dominate portfolio risk. Simple but risk-inefficient. 2. **Minimum Variance** — concentrates in low-volatility assets, creating extreme sector tilts. Minimizes total risk but distributes it unevenly. 3. **ERC** — a compromise that diversifies risk sources without minimizing total risk. Every asset is an equally important contributor. **Practical Considerations:** - ERC requires a reliable covariance matrix estimate — estimation error directly affects weight accuracy - The optimization is non-linear and typically solved numerically using gradient descent - ERC portfolios tend to underweight high-volatility assets (like minimum variance) but less extremely - Turnover is moderate (20-30% annually) as covariance structures evolve slowly - In equity-only contexts, ERC produces lower Sharpe ratios than minimum variance but higher diversification ratios ERC is the equity-specific application of the broader risk parity concept (which spans asset classes). See our CFA Level II Equity module for risk-based allocation techniques.

What is an Equal Risk Contribution portfolio, and how does the allocation methodology differ from equal weighting or minimum variance?

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