1. Set the comparison
For each product–campaign row, supply the expected units without the offer and the gross units sold with the offer. Baseline units are multiplied by promotion days divided by baseline days when both day fields are provided. A day-count adjustment does not correct seasonality, trend, product availability, or a different customer mix.
2. Calculate contribution
Baseline contribution = aligned baseline units × (regular price − variable unit cost)
Promotion contribution = gross promotion units × (promotion price − variable unit cost) − returned units × promotion price − fixed campaign spend + supplier funding − later displaced units × regular unit contribution
Contribution change = promotion contribution − baseline contribution
Variable unit cost should include product cost and relevant per-unit fulfilment and payment costs. Fixed campaign spending and supplier support are allocated once across product rows. Support already deducted from unit cost should not be entered again as funding.
3. Decompose the change
- Volume: change in gross units valued at the original regular unit contribution.
- Price: all gross promotion units valued at the difference between promotion and regular prices.
- Unit cost: promotion units valued at the difference between original and scenario variable costs.
- Refunds: full refunded revenue, with variable costs conservatively unrecovered.
- Later displacement: supplied lost future units valued at regular unit contribution.
- Spend and funding: allocated incremental fixed spending and supplier support.
These components sum to the contribution change. This is an accounting bridge, and its ordering does not identify separate causal mechanisms.
4. Solve for break-even response
The minimum gross promotion volume must recover baseline contribution plus fixed campaign spending minus funding. The calculation holds observed refund and supplied displacement rates constant as volume changes. When contribution per extra unit is nonpositive, more volume may deepen a loss; a minimum-volume target is then undefined or funding can create a maximum viable volume.
5. Inspect uncertainty
The scenario studio varies gross promotion units, promotion price, promotion unit cost, spending, funding, and expected baseline units. Price and volume are independently varied. A price slider does not predict demand; use a defensible demand estimate and set volume accordingly.
Limits that matter
- All comparisons depend on the supplied baseline. They do not establish a causal treatment effect.
- Fixed overhead, financing, income tax, and unrecorded product spillovers are excluded.
- Baseline refunds are not separately modeled. If expected no-promotion refunds are material, use a fuller baseline model rather than relabeling gross units.
- Missing displacement is marked unmeasured and excluded from the arithmetic; it is not evidence of no displacement.
- Portfolio percentages are calculated from totals, rather than an unweighted average of row percentages.
- All inputs in a project must share one currency. Currency labels do not convert exchange rates.
- The campaign workbench produces sensitivity comparisons rather than statistical confidence intervals. The separate experiment studio offers model-based intervals under explicit design assumptions; neither workspace guarantees future revenue.