# Contribution Margin Ratio Drift Review

Review a shifting contribution margin ratio before applying it to a new period.

## Scope
Preparation and review only. No account action or professional decision.

## Inputs
Two or more periods of sales, variable costs and the ratio in use.

## Workflow
1. Compute the ratio for each period.
2. Compare against the ratio in use.
3. Flag a ratio in use that predates a cost or price change.
4. Return the drift review without a forecast claim.

## Output contract
period | sales | variable | ratio | ratio_in_use | drift | forecast_unproved

## Fictional acceptance test
Fictional periods show ratios 0.60 and 0.52 after a cost rise; planning still uses 0.60. On 10,000 planned sales the stale ratio overstates contribution by 800.

## Review gates
Keep original values, source IDs and version dates. Unknown facts stay held. Use qualified review for hiring, legal and accounting conclusions. No send, share, sign-in, scheduling, ledger change or payment. Fictional contract review is not a live account compatibility test.

## Method source
https://corporatefinanceinstitute.com/resources/accounting/contribution-margin-overview/

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