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Use the opposed original pair
Weights 40/60, standard deviations 20%/10% and correlation −1 give total volatility 2%. Weighted Euler components are +8 and −6 percentage points. Both asset capital weights remain positive.
Compare signed and absolute sums
| Calculation | Result | Meaning |
|---|---|---|
| 8 + (−6) | 2 percentage points | Signed volatility decomposition |
| |8| + |−6| | 14 percentage points | Sum of component magnitudes |
| 8 / 2 and −6 / 2 | 400% and −300% | Signed shares of total volatility |
Choose a display that keeps signs
A positive-only pie cannot represent the negative component. Use a signed table or bar display and label the component unit. If a separate magnitude metric is useful, define it separately rather than renaming it total volatility.
Check the denominator before shares
At exact cancellation total volatility is zero and these volatility share ratios are undefined. A zero total does not justify creating arbitrary positive shares to fill a chart.