Source: https://guthlabs.ai/docs/instruments/inflation-adjuster-cpi/implementation/

instrument implementation / implementation-contract

# Inflation Adjuster (CPI) implementation

A source-bound implementation contract for Inflation Adjuster (CPI); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-017

**Effect**: Computation or source lookup only

## Input and validation requirements

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.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "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%."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/inflation-adjuster-cpi/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/inflation-adjuster-cpi/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/inflation-adjuster-cpi/qualification/>)

## 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`