Real vs Nominal Return implementation

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

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