Risk Parity & Equal Risk Contribution (ERC) Lab
Model covariance risk budgeting, the 60/40 risk illusion, leverage scaling, and All-Weather diversification.
Bridgewater All Weather: Classic 4-asset risk-balanced framework with negative equity-treasury correlation, demonstrating how low-volatility bonds receive higher capital allocations to balance risk.
Parameters
Matrix 1: Equity Volatility vs Bond Volatility on Risk Parity Treasury Weighting (%)
Matrix 2: Equity-Bond Correlation vs Target Volatility on Required Leverage Multiple ($x$)
Institutional Theory: Risk Parity & Covariance Budgeting
1. The 60/40 Risk Illusion & Marginal Contribution
In standard Mean-Variance Optimization and naive 60/40 portfolios, dollar capital allocation is mistaken for risk diversification. Total portfolio volatility is Euler-decomposed into marginal risk contributions:
Because $\sigma_{\text{eq}} \approx 2.5 \times \sigma_{\text{bond}}$, in a 60/40 portfolio $\text{RC}_{\text{eq}} / \sigma_p > 85\%-92\%$.
2. Equal Risk Contribution (ERC) Formulation
Maillard, Roncalli, and Teïletche (2010) proved that an ERC portfolio has a unique, positive solution satisfying the risk-matching condition across all asset pairs:
ERC lies strictly between Minimum Variance and Equal Weighting on the efficient frontier, maximizing the diversification ratio without needing expected return estimates.
3. Leverage Scaling & Target Volatility
Because ERC allocates heavily to low-risk assets, its unlevered volatility is typically below institutional targets. The portfolio applies leverage $L$ to scale risk to $\sigma_{\text{target}}$:
By leveraging a high-Sharpe balanced core, Risk Parity achieves superior risk-adjusted returns compared to concentrating risk in unhedged equities.
4. The All Weather Macro Economic Framework
Bridgewater's Ray Dalio structured Risk Parity across four macroeconomic environments, mapping specific asset classes to economic surprises:
By equalizing risk across all four quadrants, the portfolio survives regime shifts without relying on predictive macro timing.
Quantitative Mastery Quiz
1. Why does a traditional 60% Equity / 40% Bond portfolio suffer from the "Risk Illusion"?
2. What exact mathematical condition defines an Equal Risk Contribution (ERC) portfolio?
3. Why do institutional Risk Parity funds typically employ leverage?
4. What occurs when stock-bond correlation flips from negative to strongly positive (e.g., during inflation shocks)?
Frequently Asked Questions
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