T_gap — Transparency Gap Index
T_gap = (AidData Hidden Debt + LGFV Liabilities) / Official External Debt
If T_gap > 1.5 → credit rating is fiction. China LGFV: T_gap ≈ 2.8. Pakistan: T_gap ≈ 1.9. Laos: T_gap ≈ 3.1. 2026 USD squeeze makes T_gap actionable immediately — hidden debt denominated in USD is now unpayable.
Source: AidData CDFP + IMF WEO official debt tables
V_res — Resource Vulnerability Score
V_res = (Food Import %) × (Aquifer Depletion Rate) × (Fertilizer Price Index)
2026 shock: Fertilizer +31% this month. Countries with low groundwater (Pakistan V_res: EXTREME, Egypt V_res: CRITICAL) now face Debt-for-Food spiral — must borrow just to prevent famine. This is the food-debt cascade trigger.
Source: FAO FAOSTAT + GRACE-FO + FAO AMIS fertilizer prices
Δ_phys — Physical/Fiscal Divergence
Δ_phys = ΔNighttime Light Intensity / ΔReported GDP Growth
If Δ_phys < 0.7 → government overstating growth to stay in IMF programme. April 2026 NASA study confirms nighttime light volatility is near real-time societal shock indicator: protests, blackouts, civil unrest precede official reports by weeks.
Source: NASA Black Marble VNP46 daily + IMF/World Bank GDP
Reserve Runway Formula
Reserve Runway (days) = Total FX Reserves / Daily Import Bill
IMF convention crisis threshold: < 90 days. Red Zone: < 30 days. As of April 2026: Pakistan < 30 days, Laos < 15 days, Ethiopia < 20 days. Sri Lanka hit zero in 2022 — this signal was visible 18 months prior.
Source: IMF IFS data.imf.org/IR + World Bank import data
S_ratio — Sovereignty Survival Ratio
S_ratio = (GDP Growth Rate) / (Debt Service + Import Cost) × γ₁ floor proximity
When S_ratio < 1.0, the country cannot service its obligations from current output. It must borrow or print. Below γ₁ floor, the system enters the transmission zone — stress transfers to adjacent sovereigns.
Source: Derived from IMF WEO + AidData + GRACE-FO. γ₁ = 14.134725141734693