How does risk budgeting work in practice for asset allocation?

Question

AcadiFi · Accepted Answer

Risk budgeting flips the traditional approach on its head: instead of deciding 'how much money goes into each asset class,' you decide 'how much risk each asset class is allowed to contribute to the portfolio.'

**Key Concept: Marginal Contribution to Total Risk (MCTR)**

Each asset class contributes to the portfolio's total risk based on:
- Its weight in the portfolio
- Its volatility
- Its correlation with the rest of the portfolio

The formula for each asset's **Absolute Contribution to Total Risk (ACTR):**

ACTR_i = w_i × β_i × σ_portfolio

Where β_i is the asset's beta relative to the portfolio.

**Example: Three-Asset Portfolio**

| Asset | Weight | Beta to Portfolio | Portfolio σ = 10% |
|---|---|---|---|
| US Equities | 50% | 1.3 | ACTR = 0.50 × 1.3 × 10% = 6.5% |
| US Bonds | 30% | 0.4 | ACTR = 0.30 × 0.4 × 10% = 1.2% |
| Real Estate | 20% | 1.15 | ACTR = 0.20 × 1.15 × 10% = 2.3% |
| **Total** | 100% | | **10.0%** |

**Interpreting the Risk Budget:**
- US Equities consume 6.5% / 10.0% = **65% of the risk budget** despite being only 50% of capital
- US Bonds consume only **12% of the risk budget** while holding 30% of capital
- Real Estate consumes **23% of the risk budget** at 20% of capital

**Active Risk Budgeting:**
For portfolios managed against a benchmark, you can also budget *active risk* (tracking error). If you have 3% of active risk budget:
- 1.5% might go to equity selection (stock picking)
- 0.8% to sector tilts
- 0.7% to currency bets

**Optimal Risk Budgeting (Equal Marginal Risk):**
The optimal allocation is where the ratio of expected excess return to MCTR is equal across all asset classes. If one asset has a higher ratio, you're not being compensated efficiently and should shift capital toward it.

**Practical Value:**
Risk budgeting prevents the common mistake of thinking a '60/40 portfolio' is well-diversified. In reality, the equity portion often contributes 85–90% of total risk. Risk budgeting makes this transparent and actionable.

For more on portfolio construction frameworks, explore our CFA Level III course.

How does risk budgeting work in practice for asset allocation?

Master Level III with our CFA Course

Related Questions

Related Articles

Practice Questions