Make the two periods comparable
A mix bridge is useful only when both periods use the same product mapping, currency, indirect-tax treatment, return and fee boundary, and contribution definition. New or retired products need an explicit mapping rather than being forced into an old row.
Evidence to reconcile
- Baseline and revised period with the same duration or a documented normalisation. (not complete)
- Units, realised net price and included variable unit cost for each product. (not complete)
- Returns, discounts, channel fees and indirect tax on the same basis. (not complete)
- Product mapping for renamed, bundled, new or retired items. (not complete)
- Capacity or scarce-resource units when the mix competes for constrained capacity. (not complete)
- Rounding and unexplained residuals retained as explicit rows. (not complete)
| Measure | Unit | Boundary |
|---|---|---|
| Product volume | Units per product per period | Matched product mapping |
| Net price | CU per unit | After included discounts/returns on stated tax basis |
| Variable unit cost | CU per unit | Same included cost stack in both periods |
| Product contribution | CU per product per period | Units × unit contribution |
| Portfolio contribution rate | Percentage of portfolio revenue | One portfolio denominator |
Build product rows before the portfolio total
Product contribution = units × (net price - included variable unit cost); portfolio contribution = sum(product contributions); portfolio contribution rate = portfolio contribution ÷ portfolio revenue
- units
- Realised or scenario units for one mapped product in the period (units per period) — sales record or user scenario
- net price
- Realised price on the declared discount, return and tax basis (CU per unit) — sales record or user scenario
- included variable unit cost
- Variable costs inside the selected contribution boundary (CU per unit) — business cost record or user scenario
- portfolio revenue
- Sum of product units multiplied by their net prices (CU per period) — calculated output
Mix-only contribution = sum(revised units or shares × baseline unit contribution)
- revised units or shares
- Revised sales composition applied to a stated total-volume basis (units or percentage of units) — revised record or user scenario
- baseline unit contribution
- Baseline net price less baseline variable unit cost for each mapped product (CU per unit) — baseline business record
Holding baseline price and cost constant isolates an arithmetic mix effect. It does not identify its behavioural cause.
- Reconcile product mapping and one contribution boundary across both periods.
- Calculate net price, variable unit cost and unit contribution for every product.
- Calculate baseline and revised revenue and contribution by product.
- Apply revised units to baseline unit contribution to construct the mix-only view.
- Separate price, cost and quantity effects rather than assigning the full change to mix.
- Reconcile the driver rows to the total contribution change and preserve any residual.
- Review capacity, demand, strategic role and cash constraints before changing assortment.
Worked example: revenue rises while contribution rate falls
Fictional monthly CU scenario, tax excluded. Prices and unit costs are unchanged so the example isolates quantity and mix.
| Product row | Baseline period | Revised period |
|---|---|---|
| Product A inputs | 100 units; price 100; variable cost 55 | 80 units; price 100; variable cost 55 |
| Product A revenue | 100 × 100 = 10,000 CU | 80 × 100 = 8,000 CU |
| Product A contribution | 100 × 45 = 4,500 CU | 80 × 45 = 3,600 CU |
| Product B inputs | 100 units; price 60; variable cost 45 | 220 units; price 60; variable cost 45 |
| Product B revenue | 100 × 60 = 6,000 CU | 220 × 60 = 13,200 CU |
| Product B contribution | 100 × 15 = 1,500 CU | 220 × 15 = 3,300 CU |
| Portfolio revenue | 16,000 CU | 21,200 CU: up 5,200 CU |
| Portfolio contribution | 6,000 CU | 6,900 CU: up 900 CU |
| Contribution rate | 6,000 ÷ 16,000 = 37.5% | 6,900 ÷ 21,200 ≈ 32.5% |
Test the branches that can change the interpretation
| Branch | Recalculate | Decision boundary |
|---|---|---|
| Price | Hold revised units; apply revised realised prices. | Separate discount or price effect from mix. |
| Unit cost | Hold revised units; apply revised variable costs. | Do not label supplier or waste change as mix. |
| Returns and fees | Rebuild net price and unit cost on the same event boundary. | A channel shift may alter retained contribution. |
| Capacity | Divide unit contribution by the scarce resource used. | A high unit contribution can rank lower per constrained hour. |
| Demand downside | Reduce revised volume without changing unit economics. | The bridge does not forecast whether the new mix persists. |
Choose the next analysis, not an automatic winner
Decision checkpoints
- Price effect: review realised price and discount records. (not complete)
- Cost effect: review purchase, usage, return and fee records. (not complete)
- Mix effect: test product roles and a deliberate alternative mix. (not complete)
- Capacity constraint: compare contribution per scarce unit. (not complete)
- Residual: leave unexplained until the records reconcile. (not complete)
- Discontinuation: review avoidable costs, demand, customer role and fixed-cost effects separately. (not complete)
Product-mix questions
- Can revenue rise while total contribution falls?
- Yes. A sufficiently large shift toward lower or negative contribution, or a price/cost change hidden inside the comparison, can reduce total contribution as revenue rises.
- Should the business prioritise contribution rate or total contribution?
- Neither metric is universally sufficient. Compare total contribution, rate, fixed-cost coverage, capacity, cash and strategic constraints on the same scenario.
- Should the lowest-contribution product be discontinued?
- Not from this bridge alone. Review avoidable costs, constrained resources, demand, customer relationships and the effect on other products.
Sources and methodology boundary
- Contribution margin per unit, ratio and total — OpenStax: Supports stable contribution-margin structure; instructional examples are not benchmarks.
- Multi-product sensitivity under a changing sales mix — OpenStax: Supports product-specific contribution and the requirement to revise analysis when mix changes.
- Decisions when resources are constrained — OpenStax: Supports contribution per limiting resource; it does not prescribe demand or assortment choices.