Source: https://guthlabs.ai/docs/instruments/real-vs-nominal-return/implementation/

instrument implementation / implementation-contract

# Real vs Nominal Return implementation

A source-bound implementation contract for Real vs Nominal Return; 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**: t4-128

**Effect**: Computation or source lookup only

## Input and validation requirements

The formula has a hard singularity at inflation = -100%, requiring explicit input rejection. It also has no documented branch behavior around that singularity and is vulnerable to a 100-times scale error if percentage inputs are interpreted as decimal rates.

## 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": {
    "nominal_return_pct": 8,
    "inflation_rate_pct": 3
  },
  "expected_outputs": {
    "real_return_pct": 4.85436893
  },
  "working": "Convert percentages: nominal=8/100=0.08; inflation=3/100=0.03. Compute real=(1+0.08)/(1+0.03)-1=1.08/1.03-1=108/103-1=5/103=0.0485436893. Convert to percent: 0.0485436893*100=4.85436893%."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/real-vs-nominal-return/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/real-vs-nominal-return/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/real-vs-nominal-return/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-tranche4/tranche4-results.json`