Inflation Adjuster (CPI) mechanism

Model scope

The arithmetic and CPI-ratio method are correct under the stated annual-average CPI-U convention. Final release requires explicit resolution of the meaning of real_value, the exact CPI series and annual/monthly convention, the cumulative-inflation formula, and behavior for unavailable future years.

• The CPI ratio formula is standard for converting an amount from base-year dollars into equivalent target-year dollars: amount × CPI_target/CPI_base.
• The output name real_value is potentially misleading: this formula produces an inflation-adjusted nominal equivalent in target-year dollars, not a real value unless the direction and base of comparison are explicitly defined.
• The specification does not give the formula for cumulative inflation percentage; it should be (CPI_target/CPI_base - 1) × 100%.
• The CPI series definition is incomplete: it must explicitly specify CPI-U, U.S. city average, all items, annual average index, and the 1982-84=100 base. Monthly or December CPI values would produce different results.
• Future-year adjustment is not computable from a historical lookup table unless a forecast CPI table is separately supplied; the instrument should reject unavailable future years or clearly label forecast assumptions.

Units and conventions

• amount is a monetary amount in consistent currency units, such as U.S. dollars; the formula does not convert currencies.
• CPI values are dimensionless index numbers, so CPI_target/CPI_base is dimensionless.
• The table is assumed to be U.S. CPI-U, U.S. city average, all items, annual average, with 1982-84=100.
• base year and target year refer to annual-average CPI years, not specific months.
• CPI values must be positive and present in the selected table vintage.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "amount_usd": 100,
    "base_year": 1983,
    "target_year": 2023
  },
  "expected_outputs": {
    "inflation_adjusted_amount_usd": 304.702,
    "cumulative_inflation_percent": 204.702
  },
  "reference_data": {
    "cpi_u_annual_average_1983": 100,
    "cpi_u_annual_average_2023": 304.702,
    "source_convention": "Official BLS CPI-U annual-average historical table; U.S. city average, all items, 1982-84=100"
  },
  "working": "CPI ratio = 304.702 / 100.000 = 3.04702. Inflation-adjusted amount = $100.00 × 3.04702 = $304.702. Cumulative inflation = (3.04702 - 1) × 100% = 204.702%."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

An invalid or missing base-year lookup can produce CPI_base = 0 or an undefined CPI value; calculating instead of rejecting causes division by zero or an undefined result. The direction of the amount conversion is also convention-sensitive unless the interface clearly states that the amount is denominated in the base year and converted to the target year.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche7/tranche7-results.json
• BOUNDARY_HAZARD_CATALOG.json