Source: https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/implementation/

instrument implementation / implementation-contract

# GDP Growth Rate Calculator implementation

A source-bound implementation contract for GDP Growth Rate Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_WITH_ERRATA**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-with-binding-errata

**Evidence ID**: t5-172

**Effect**: Computation or source lookup only

## Input and validation requirements

The calculator specification has an undefined-result failure when the prior GDP is zero and does not state a required validation response. It also leaves the annualization branch and sign-reporting conventions insufficiently explicit, creating risks of incorrect results or interpretation.

## Required corrections

````
[
  {
    "vector": 2,
    "field": "annualized_growth_pct",
    "wrong": -9.6311109375,
    "correct": -9.631210938,
    "cause": "0.975^4 transposed digits (0.90368889 vs 0.90368789)"
  }
]
````

## Inspectable interface fixture

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

````
{
  "inputs": {
    "GDP_t": 20200,
    "GDP_t_minus_1": 20000,
    "units": "billions of currency units",
    "frequency": "quarterly",
    "basis": "real GDP",
    "periods": "consecutive quarters"
  },
  "expected_outputs": {
    "growth_pct": 1,
    "annualized_growth_pct": 4.060401
  },
  "working": "growth = (20,200 - 20,000) / 20,000 = 200 / 20,000 = 0.01; 0.01 × 100 = 1%. annualized = ((20,200 / 20,000)^4 - 1) × 100 = (1.01^4 - 1) × 100 = (1.04060401 - 1) × 100 = 4.060401%."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/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-tranche5/tranche5-results.json`

- `tranche errata record`