How our UK Cost Index is compiled
A transparent account of how we research, sample, validate and refresh the average car insurance premium figures on this site.
Phase 1 — Until Q3 2026
While we build our own primary data pipeline, the Cost Index draws on two authoritative published UK sources:
- ABI Motor Insurance Premium Tracker — a 28-million-policy dataset published quarterly. National-average figures (e.g. £604 35yo male, £560 all comprehensive Q1 2026) come from here.
- Confused.com Premium Index — a 250,000-quote dataset, also quarterly. We use it for cross-validation and regional-spread inputs.
Age-banded and regional figures combine ABI national averages with published demographic averages from NimbleFins, MoneyHelper and broker-published age-band data. Cross-validation across three sources before publication.
Phase 2 — From Q3 2026
The index transitions to primary network data: quote requests originating through carinsuranceexpert.co.uk. Outliers above the 99th percentile are excluded. Comprehensive cover only; private use; all vehicles unless otherwise specified.
Sampling rules
- Comprehensive cover only — third-party and TPFT excluded
- Private use — taxi, courier, business-use heavy excluded
- Standard mileage — figures assume 8,000–12,000 annual miles
- UK postcodes — England, Scotland, Wales; Northern Ireland excluded (different market structure)
Refresh cadence
Quarterly — every February, May, August and November. The dateModified field on each page reflects the most recent refresh. Major regulatory changes trigger out-of-cycle updates as needed.
Citation
Our datasets are available under CC BY 4.0 for editorial citation with attribution: "Car Insurance Expert UK Cost Index, [period]". Bespoke breakdowns and custom dataset extracts: editorial@carinsuranceexpert.co.uk.
Confidence intervals
Where we publish a single figure (e.g. "average premium for 17-year-olds is £2,847"), the true population average sits within ±£200 of the published figure at 95% confidence based on ABI sample sizes. Where we publish ranges (e.g. £604–£842), these reflect the actual range of typical quotes for the cohort.
Last updated: 25 May 2026