GeraClinic / GP List Size Index / Methodology
How the Gera GP List Size Index is calculated
The Gera GP List Size Index is a reproducible 100-based index derived entirely from the real NHS England Quality and Outcomes Framework (QOF) 2024-25 registered-list-size figures. This page sets out the exact formula, a worked example, the data provenance and the limitations — so anyone can reproduce or challenge the number.
What the index measures
The index answers one question: how large is the GP-registered patient population in each part of England? It uses the single official QOF measure — an ICB’s registered patient list size (every patient registered at its GP practices) — and expresses it as a 100-based number, where 100 is an exactly average-sized ICB and higher means a larger registered list.
The official measure: QOF “list size” is the count of all registered patients — the same register-wide denominator NHS England uses for its prevalence indicators. It is not a performance or quality score.
The formula
Registered list size, scored against the national-average ICB
Take the published QOF registered list size for an ICB and divide it by the national mean ICB list (national total ÷ 42 ICBs), then multiply by 100. The national mean is the only reference point, and it is disclosed here. There is no weighting and no hidden adjustment.
GLSI = round(100 × icbListSize / 1,518,254)
(national mean ICB list = 63,766,671 / 42 = 1,518,254)
Worked example — Greater Manchester, 2024/25 (QOF)
- Registered list size: 3,301,785 patients (real QOF 2024-25 figure).
- GLSI = round(100 × 3,301,785 / 1,518,254) = 217
An index of 217 means Greater Manchester’s registered list is about 2.2× the size of the average English ICB.
The national workload context (a second, labelled source)
To explain why list size matters, the hub page shows national GP-workload figures from a different NHS release — the General Practice Workforce statistics: about 1,676 registered patients per full-time-equivalent GP (median 1,747 per practice, April 2026), with 28,777 fully-qualified FTE GPs at 31 December 2025. These figures are NOT part of the per-ICB index calculation and are always labelled as workforce context. The national average of about 10,305 registered patients per practice is the QOF total (63,766,671) divided by the 6,188 QOF practices, so it stays consistent with the same release the index uses.
Data provenance
Every ICB list size is the real published QOF 2024-25 figure, summed to ICB level from the published practice/sub-ICB rows. The 42 ICBs sum to the published national total of 63,766,671. The index (the scaling) is the only Gera-computed layer and is fully specified above.
Contains public sector information published by NHS England and licensed under the Open Government Licence v3.0. Source: NHS England — Quality and Outcomes Framework (QOF) 2024-25 (registered patient list size) (2024/25, published 28 August 2025).
Contains public sector information published by NHS England and licensed under the Open Government Licence v3.0. Source: NHS England — General Practice Workforce (31 December 2025 / 30 April 2026) (2025-26, published 2026).
No-fabrication policy
Only real published QOF list sizes are shown. Where a figure is derived (the national mean ICB list, the per-practice average, the index itself) it is computed transparently from the published totals with the formula given above — never estimated or imputed. Gera does not display a figure it has not traced to the NHS source.
What the index does NOT show
- It is a measure of population size, not quality, access or waiting times. A larger list is not automatically “worse” care.
- It covers England only and is reported at ICB level — it is not a rating of any individual GP practice.
- Registered list size can differ slightly from resident population (list inflation, cross-boundary registration); QOF uses the registered count.
- It is an annual summary from QOF. For appointment access and waiting times, see the related Gera indices linked on the hub page.
- This page is information, not medical advice. For any decision about your own care, use NHS 111 or speak to a clinician.
Update cadence
NHS England publishes QOF annually. Gera recomputes the index on each release. The current figures are for 2024/25 (QOF) and were last recompiled on 3 July 2026.