The Metra methodology is a two-layer public corpus, published here in full and intended to be read, audited, critiqued, and attested by credentialed actuaries. Each layer is version-pinned and separately attestable.
Current public corpus
Reviewers evaluating the full instrument should start with the Complete Actuarial Brief; the versioned documents below are the pinned, citable layers. Attestations are version-pinned per layer.
Exposure layer — Methodology v1.1 · current
The current Exposure layer specification: BMI economic pathway ($93/BMI-point/person-year, Thorpe & Joski 2024, proposed — pending actuarial review), versioned coefficient register with status lifecycle, eligibility rules (age 24–64, ESI, baseline BMI 30.0–45.0, credit floored at BMI = 30), deterministic digest-seeded bootstrap CI (B = 10,000), bidirectional marker visibility (never-silent principle), and HbA1c conditional module (disabled pending actuarial acceptance). BP, glucose, and waist are non-monetised signal-only markers — the legacy per-unit coefficients ($68/lb, $150/mmHg, $50/mg-dL, $30/cm) are all retired in v1.1. No Bühlmann credibility blend, no lag haircut, and no attrition projection are applied within the v1.1 exposure engine. Supersedes v1.0 (pinned historical).
Exposure layer — Methodology v1.0 · pinned historical
The original Exposure layer: cohort construction and exposure units, Bühlmann credibility (k = 400 PQ), per-marker exposure with percentile-bootstrap CIs (B = 10,000), the four-marker additive coefficient register ($68/lb weight · $150/mmHg BP · $50/mg-dL glucose · $30/cm waist). Published and version-pinned as history; superseded by v1.1 for the current Exposure layer. Separately citable and attestable.
Experience Calibration layer — Methodology v2.1 · current (v2.0 pinned historical)
The additive Experience Calibration layer: take the group's own paid medical and Rx experience, mature it to an incurred basis (completion factor or IBNR), pool large claimants, and credibility-blend the observed per-employee rate against the carrier manual rate (Bühlmann Z = N/(N+400), the constant k = 400 derived as an independent full-credibility anchor). The blended rate is projected forward under trend and attrition, then the forward metabolic signal from the current Workforce Exposure Forecast (v1.1) is applied as a disclosed dollar offset — returning a projected forward claims figure with two labeled uncertainty bands: an expected-claims confidence band and a realized-paid predictive interval. The v2.1 mathematical specification was written against v1.0; in production the offset M is now the v1.1 exposure point estimate. The two credibility weightings are kept disjoint and never stacked. v2.1 is additive to v2.0, which remains published and version-pinned.
Complete Brief — all layers in one document
The whole corpus in a single document for the reviewer who wants the full picture without assembling it from the version-pinned parts: the v1.0 Exposure layer, the v2.0/v2.1 Experience Calibration layer, and the attestation framework, each presented as a clearly labeled part with its version pinning preserved.
Reading guide
A short reading guide for the methodology document, written for the actuary preparing to read it ahead of a renewal or strategy meeting. Anticipated reviewer questions, the seven most-frequently-raised technical objections and their responses with section references, a pre-meeting checklist, and a post-meeting follow-up template. The companion is a reading aid; it adds no methodology of its own.
Attestation roster
The list of credentialed actuaries who have read this methodology at the published version and attested to its defensibility. Each entry carries the actuary's name, credential, firm, the methodology version attested, and the attestation date. Attestations are version-pinned; a version bump requires re-attestation. Compensation arrangements, where any exist, are publicly disclosed alongside each entry.
Sample output
A complete generated Workforce Exposure Forecast PDF for a representative 322-employee employer cohort, produced from the demonstration corporate population on the Metra platform. The Sample carries an illustrative Demo Signer block (Marcus Chen, FSA, MAAA — Chen Actuarial Consulting), which is a demonstration entry and not a live signing engagement; the published roster on the attestations page shows this entry as a clearly marked demonstration signer with live engagement pending. The Sample shows the cover, executive summary, BMI economic exposure breakdown with bootstrap CIs, workforce-risk intelligence (multi-marker bidirectional movement), and the methodology-version footer. Useful as a reference for what the buyer-side v1.1 instrument looks like at the renewal table. Note: if the sample PDF on file predates this corpus publication it is a v1.0-era demonstration; a v1.1 sample will be regenerated from the updated engine.
Companion document
Pinned historical — v1.0 era. The doctrine-register companion piece for the original four-marker additive methodology (v1.0): per-marker cost coefficients with full citations, conservatism-and-stacking rationale, and the appendix introducing the multi-marker move from the original single-marker (weight-only) framing. Useful background for reviewers who want to understand the lineage of the v1.0 coefficients and why the four-marker additive model was retired in v1.1. Note that the $68/lb, $150/mmHg, $50/mg-dL, and $30/cm coefficients documented here are superseded in the current v1.1 corpus.
For credentialed actuaries
If you hold an ASA, FSA, MAAA, FCAS, or ACAS credential and are reading this document professionally, you are the intended primary audience. Critiques, corrections, and counter-derivations are welcomed and inform the next version. Attestation submissions and review correspondence for the current Exposure layer (v1.1): care@usemetra.com, subject line “Methodology Review — v1.1” or “Methodology Attestation — v1.1”.