1. Objective
The ISI measures the concentration of external dependencies for each EU-27 member state across a set of strategic axes. It does not assess quality, risk, or desirability of those dependencies — only their structural concentration.
2. Scoring Framework
Each axis produces a score on the [0, 1] interval using a Herfindahl-Hirschman Index (HHI) framework:
- 0.00 — Perfectly diversified (equal shares among infinite partners)
- 1.00 — Total concentration (100% from a single source)
| Range | Classification |
|---|---|
| ≥ 0.50 | Highly Concentrated |
| 0.25 – 0.49 | Moderately Concentrated |
| 0.15 – 0.24 | Mildly Concentrated |
| < 0.15 | Unconcentrated |
3. Composite Aggregation
The ISI composite is computed as an unweighted arithmetic mean of all available axis scores for each country:
No domain-weighting is applied. This is a deliberate design choice — the index does not presume which axes matter more. Users should consider axis-level scores when domain-specific analysis is needed.
4. Data Pipeline
All data is pre-materialized by the backend export pipeline (export_isi_backend_v01.py) and served as static JSON artifacts by the API layer (isi_api_v01.py). The frontend performs zero computation — it is a pure rendering layer.
5. Axis-Level Documentation
Each axis has its own measurement definition, data sources, inclusion/exclusion scope, and known limitations. These are documented on the individual axis detail pages, which are driven entirely by the backend axis registry.