Sovereign Stress Index
Formula
SSI = 0.35×(CDS Spread Z) + 0.25×(10Y-2Y Spread Z) + 0.25×(FX Vol Z) + 0.15×(Debt/GDP Z)
- CDS Spread Z – 5-year sovereign CDS spread normalised to global EM distribution
- 10Y-2Y Spread Z – Yield curve slope (can invert during stress), Z-scored over 10-year history
- FX Vol Z – Currency implied volatility, normalised; higher = more stress
- Debt/GDP Z – Sovereign debt-to-GDP ratio, normalised against peer EM benchmark
Why It Matters
No single sovereign stress signal is reliable in isolation. CDS spreads can be illiquid; yield curves distorted by QE; FX volatility driven by global risk-off. By compositing four independent signals with empirically-derived weights, the SSI is more robust than any single-factor measure. The index is designed to be comparable across countries and time periods, making it suitable for cross-sovereign portfolio risk assessment.
Institutional Use
Analogous to the IMF's "Vulnerability Exercise for Emerging Markets" composite scoring. Rating agencies construct similar multi-factor stress indices for their sovereign rating watches. The ECB's Financial Stability Review uses equivalent composites for euro area peripheral country monitoring.