Trade Promotion ROI: The Math Most Brands Skip

ShopperExperts · August 27, 2026

For most mid-size CPG brands, trade promotion is the largest expense after the product itself — and the least examined, because measuring it requires an uncomfortable ingredient: a baseline. Without knowing what would have sold anyway, every promo report is a story with a happy ending.

The Baseline Is the Whole Game

Incremental volume = promo-period sales minus baseline. The baseline is the item's normal velocity in those stores and weeks — seasonality included — computable from store-level history. It doesn't need to be perfect; it needs to exist and be applied the same way every time. A promo that "sold 10,000 units" but baselines at 8,500 bought 1,500 incremental units, and the ROI math starts there, not at ten thousand.

The Three Quiet Costs

• Subsidized volume: those 8,500 baseline units all sold at the discounted margin. That's margin you paid on sales you already had — usually the largest hidden line.
• Pantry loading: the sales dip after the promo is shoppers consuming what they stockpiled. Measure the weeks after; the dip belongs in the promo's ledger.
• Deal-training: run the same discount every six weeks and shoppers — and buyers — learn to wait for it. Your baseline quietly becomes the promoted price. Hard to see promo-by-promo, unmistakable across a year of them.

What Changes When You Run the Math

Not the total budget, usually — retailers expect the spend. What changes is the mix: money migrates from deep discounts on items that would have sold anyway toward display and placement on items with real velocity headroom, and toward accounts where incrementality actually shows up. Even a rough event-by-event ROI ranking beats the alternative, which is negotiating next year's trade plan from anecdotes. It's a standing module in our Health Check because the data is nearly always already there — unexamined.