Scenario IRMAA surcharge tier years

Count of projection years whose IRMAA tier is above 0.

Field: Years in an IRMAA surcharge tier Unit: count Basis: no dollar basis Computed by: Engine Status: Complete chain

Appears in: scenarios-page (Medicare table "Years in a surcharge tier")

Calculation records

• Scenario comparison: years in an IRMAA surcharge tier Composition record, justified by derivation

  Purpose: How many projection years sit strictly above IRMAA tier 0, compared proposal-minus-baseline.

  Statement: For each side, surchargeTierYears = count of projection years whose published irmaaTier is strictly greater than 0 (tier 0 is the standard premium; tiers 1–5 are surcharge tiers). The comparison is the integer triple (baseline count, proposal count, proposal − baseline). Units: year counts. Rounding: none (exact integers).

  Formula: count = sum_y 1[irmaaTier_y > 0]; delta = count_proposal − count_baseline

  • irmaaTier_y: Published IRMAA tier classification for year y (unit: tier) (domain: integer 0..5)
  • count: Number of surcharge-tier years on one side (unit: years) (domain: integer >= 0)

  Timing: one count per side over that side's projection years

  Rounding: none

  Limits:

  • Medicare premium dollars and the maximum tier are different outputs; this record counts years only
  • The evidence constructs the stated irmaaTier rows rather than running two full simulations

  Provenance: derived by codex, implemented by grok.

  Independent review: cursor

  Gates (6 of 6 pass): fixture registers a test: pass; pins resolve: pass; families exist: pass; worksheet exists: pass; mutation receipt exists: pass; provenance independent: pass

  Worksheet: scenario-irmaa-surcharge-tier-years.md Mutation receipt: scenario-irmaa-surcharge-tier-years.mutation.md

  Evidence tests: comparison.evidence.test.ts

  Implemented in: comparison.ts

  Is the number of: scenario-irmaa-surcharge-tier-years

  Feeds: scenario-comparison-cell

Engine source: engine/src/scenarios/comparison.ts (ScenarioIrmaaComparison.surchargeTierYears)