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GeraClinic / NHS Staff Retention Index / Methodology

How the Gera NHS Staff Retention Index is calculated

The Gera NHS Staff Retention Index is a reproducible 0–100 score derived entirely from the real NHS England 12-month leaver rate. This page sets out the exact formula, a worked example, the population definitions, the data provenance and the limitations — so anyone can reproduce or challenge the number.

What the index measures

The index answers one question: how well is the NHS keeping its staff? It expresses the official 12-month staff retention rate — the share of staff who stayed over the year — on a 0–100 scale, where 100 means nobody left and lower means more staff left. It is published nationally, as a two-year trend, for professionally qualified clinical staff, and for the 3 NHS England regions with a published region-specific rate, so the same number is comparable across every cut.

The formula

Retention is the complement of the leaver rate

GNSRI = round1(100 − leaverRate)

That is the entire method. There is no weighting and no editorial constant — unlike most composite indices, this one applies a single, disclosed arithmetic transformation to one official statistic. The only Gera contribution is naming the retention rate and expressing it on a 0–100 scale so it is easy to quote and compare. Higher = better retention.

Worked example — England, Year to September 2024

  • Official NHS leaver rate (all staff): 10.1% for the year to september 2024
  • GNSRI = round1(100 − 10.1) = 89.9 / 100
  • Two years earlier the leaver rate was 12.5% — a retention index of 87.5 / 100 — so retention improved by 2.4 points.
  • Clinical staff, year to december 2025: leaver rate 9.4% → retention index 90.6 / 100.

Population definitions

  • All staff — all hospital and community health service (HCHS) staff. This is the population used for the national headline and the regional breakdown.
  • Professionally qualified clinical staff — a narrower clinical population, reported separately by NHS England. The two populations are never blended into one time-series; each trend uses a single, consistent population.
  • Regions — only the North West and South East NHS England regions published a region-specific leaver rate in the cited release, so only those (plus the national figure) are shown. Regions without a published rate are omitted rather than estimated.

Data provenance

Every figure the index consumes is taken directly from NHS England and NHS England Digital releases — the national and regional leaver rates from NHS England’s March 2025 workforce release, and the clinical-staff and monthly leaver rates from NHS England Digital’s NHS Workforce Statistics. No value is estimated or imputed; the retention transformation is the only Gera-computed layer, and it is fully specified above.

Contains public sector information published by NHS England and licensed under the Open Government Licence v3.0. Source: NHS England — “Staff leaving the NHS among lowest in over a decade” (12 months to September 2024, published 4 March 2025).

What the index does NOT show

  • It covers England only, and only the 12-month rolling leaver rate for NHS staff.
  • It is not a vacancy rate, a headcount, a sickness rate, or a measure of why staff left.
  • Region-specific figures exist only where NHS England published them; it is not a full per-region or per-trust league table.
  • A higher retention rate is generally positive, but the index does not judge whether a given level is “good enough” — there is no official target retention rate.
  • It is a workforce summary, not clinical or employment advice for any individual or employer.

Update cadence

NHS England Digital publishes NHS Workforce Statistics — including the 12-month rolling leaver rate — monthly, roughly six weeks after the reference month. Gera recomputes the index on each release. The figures here are for the year to september 2024 (with the freshest clinical-staff reading for the year to december 2025) and were last updated on 3 July 2026.

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