Practical framework / 5 MIN READ
Check what the promoted product gained from the rest of the portfolio
Evaluate substitution and timing before calling the sales bump incremental.
AI-assisted research and analysis for the SNS Creative Fieldbook
Sources checked 2026-11-06
A promotion can raise one product’s sales while moving purchases away from another product or an upcoming period. The evaluation needs a portfolio and time boundary that matches the business decision, rather than counting the promoted item’s increase as entirely new demand.
What you will leave with: Build a promotion outcome map covering the focal item, substitutes, complements and later periods.
Use this when
- A promoted SKU grows while neighboring products decline.
- A campaign looks successful during the offer but sales soften afterward.
This is evaluation scoping, not a universal cannibalization rate or a claim that every neighboring decline was caused by the promotion.
Define the portfolio and decision boundary
Identify the promoted item and plausible substitutes or complements based on how customers use them. Separate another item in the same company’s portfolio from a competitor’s product; the business implications differ. Include channels or stores where purchases may move if those shifts matter to the decision.
Choose a period that can capture relevant purchase acceleration and delayed outcomes. Document why the window is appropriate for the product’s buying cycle. Do not extend or shorten it after seeing a favorable pattern merely to make the promotion appear more incremental.
Distinguish sources of the sales bump
The research abstract by van Heerde, Leeflang and Wittink distinguishes cross-item effects, cross-period shifts and category expansion when decomposing promotion sales. That conceptual separation motivates a broader outcome map; its empirical averages are not a benchmark for this campaign.
List the explanations the evaluation must distinguish: switching between owned products, winning purchases from competitors, bringing future purchases forward or expanding category demand. Observed sales alone may not identify each component. Ask the analyst what comparison design and data can support the particular claims being proposed.
Measure portfolio outcomes with a credible comparison
Track focal-item and relevant portfolio outcomes using consistent units and availability conditions. Include contribution where the financial decision requires it, because shifting customers from a higher-margin item to a discounted alternative can reduce value despite stable total units. Keep returns and fulfillment differences visible.
Use a suitable counterfactual rather than simply subtracting every neighboring decline from the focal increase. Competitor changes, stockouts, seasonality and other promotions can affect the same products. A controlled design or qualified model review may help, but the assumptions and uncertainty must remain explicit.
Decide whether the promotion created worthwhile portfolio value
Present the focal result alongside total relevant portfolio value and later-period evidence. Explain which components are estimated, observed or unresolved. Avoid a precise net-incremental number when the data cannot distinguish substitution from unrelated changes.
Use the findings to refine the offer, timing or product choice within authorized scope. A promotion with cannibalization may still be useful for a legitimate strategic reason, such as a product transition, but state that reason instead of disguising transferred sales as new demand. Preserve the evaluation boundary for later comparisons.
Make the reasoning concrete.
A hypothetical promotion coincides with 100 extra units of Product A and 60 fewer units of a close substitute, Product B. The observed portfolio increase is 40 units over the chosen baseline. That arithmetic does not prove 60 units were cannibalized or that 40 were caused by the promotion.
Count the focal increase
Opening: Report 100 incremental units from the offer.
Hypothesis: The promoted item grew strongly.
Risk: Substitution, baseline validity and purchase timing are ignored.
Review the portfolio contrast
Opening: Inspect A, B, margins and later periods with a credible comparison.
Hypothesis: The analysis asks whether the business gained overall.
Risk: The causal decomposition may remain uncertain.
Report the observed portfolio pattern and seek evidence for the causal components. Do not label all focal growth incremental or all substitute decline cannibalization.
Take the questions into your next brief.
Use these prompts in your own notes. Nothing is submitted from this page.
Boundary
Which products, channels and periods matter?
Mechanisms
What substitution or timing shifts are plausible?
Comparison
What supports the no-promotion counterfactual?
Value
How do margin and fulfillment change the result?
Decision
What portfolio outcome justifies repeating the offer?
Watch for the wrong conclusion.
- Calling the promoted SKU’s full increase incremental.
- Treating every substitute decline as caused by the offer.
- Ignoring purchase acceleration into the promotion period.
- Optimizing unit volume while concealing portfolio value loss.
Your next action
Map the products and periods that could lose sales to one planned promotion, then include them in the evaluation brief.
Sources & scope
Frameworks, worksheets and hypothetical examples are original editorial synthesis. Linked primary sources support only the stated concepts. Source checking is not an independent audit of effectiveness. No named human author or reviewer is claimed.
- Van Heerde, Leeflang and Wittink: Decomposing the sales promotion bump with store data →Primary research abstract in author-institution repository · Supports: The author-institution abstract distinguishes cross-item, cross-period and category-expansion components of a promotion effect. No empirical average from the paper is generalized to the hypothetical campaign.