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

instrument / verified-with-binding-errata

# GDP Growth Rate Calculator

The current ledger marks this instrument verified with errata that must be applied at binding time.

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

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/gdp-growth-rate-calculator/qualification/>)

## Ledger state

The current ledger marks this instrument verified with errata that must be applied at binding time.

**Area**: Finance, Economics & Business (educational only — never individualized investment, tax, or legal advice)

**Tranche**: tranche-5

**Evidence ID**: t5-172

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The formulas are conditionally standard, but the specification needs explicit frequency handling, percentage-scaling behavior, multi-period semantics, positive-denominator validation, unit normalization, and a precise definition of how the real-versus-nominal flag affects inputs and labels. The honest label should state whether results are nominal or real and should identify the periods and units supplied by the user.

### Formula and scope findings

- The period-over-period formula is standard as a fractional rate, but percentage outputs require multiplying the result by 100 or explicitly formatting the fraction as a percent.

- The annualized formula is correct only for consecutive quarterly observations: (GDP_t/GDP_t-1)^4 - 1. The specification does not define behavior for monthly, annual, irregular, or non-consecutive periods.

- The phrase 'GDP values for two+ periods' does not specify whether multiple periods produce separate adjacent-period rates, a cumulative growth rate, or a compound annual growth rate.

- The real-vs-nominal flag is underspecified: the formula compares whichever GDP series is entered, but does not convert nominal GDP to real GDP or apply a GDP deflator.

- GDP levels must be on a consistent basis, including currency, scale, price basis, and seasonal-adjustment basis, before applying the formula.

### Unit assumptions

- GDP_t and GDP_t-1 are measured in the same currency, scale, price basis, and seasonal-adjustment basis; the units cancel in the ratio.

- For annualized growth, the two observations are consecutive quarters, so four compounding periods occur per year.

- The displayed percentage equals the fractional formula result multiplied by 100.

- A real GDP calculation requires real GDP inputs, typically at a stated reference-year price basis; the calculator does not itself perform inflation adjustment.

- GDP_t-1 is strictly greater than zero for both formulas to be defined.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

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.

## Errata and corrections

### Tranche errata

**annualized_growth_pct** · vector 2

-9.6311109375

-9.631210938

0.975^4 transposed digits (0.90368889 vs 0.90368789)

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

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

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

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

- `VERIFIED_LEDGER.json · VERIFIED_WITH_ERRATA`

- `evidence-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`