What is product mix
Product mix is the set of items the operation sells and, above all, each one's share of what was sold: it is the composition of sales that decides the month's result, not the size of the catalog.
The term has two meanings. The catalog mix is what the store offers — lines, brands, variety, the depth of each category. The sold mix is what went out in the period, with each item's share of revenue. The first is an assortment decision; the second is what reaches the result.
Two stores with the same revenue and the same overhead close the month in opposite ways when the sold mix is different. Each item delivers its own contribution margin index, and what pays the fixed expenses is the average of those indices weighted by each one's share.
How the mix changes the result without touching price
The calculation is a weighted average. What it shows is that shifting share between lines is worth as much as adjusting prices — and it costs the customer nothing.
item share = item revenue ÷ total revenue
average contribution index = sum of (share × contribution index of each item)
item contribution in the month = unit contribution margin × units sold
Each line's index starts with the price of one item: the selling price calculator opens up the real composition of a product and shows how much of it is left after cost, tax and commission.
Three lines in a month of R$ 360,000
Each line shows the category's share of revenue and its contribution index. The value on the right is what it delivers on its own to the store average: the share multiplied by the index.
| Beverages — 45% of revenue, 18% indexhigh turnover, thin margin, price known to the customer | 8.1 points |
|---|---|
| Grocery — 35% of revenue, 30% index | 10.5 points |
| Personal care and beauty — 20% of revenue, 48% indexlower turnover, wide margin, price rarely compared | 9.6 points |
| Store contribution indexthe weighted average of the three lines | 28.2% |
Now shift five points of share from beverages to personal care and beauty — which a change in display and in the order of the site's search results can do. The average index goes to 29.7% without a single price having been changed. On the same R$ 360,000 of revenue, that is R$ 5,400 more contribution in the month, and the operation's break-even point recedes along with it.
The mix is decided even when nobody decides it
It seems to be a consequence of what the customer wants. Half of it is a consequence of what the store displays, orders and promotes.
Endcap displays, shelf height, the order of results in the site's search, what goes in the home banner and what appears as a suggestion in the cart: each of these choices moves share from one line to another. When they are made out of habit or under supplier pressure, the mix is still being decided — only by someone who does not answer for the month's result.
The useful distinction is between traffic items and margin items. The first is the item whose price the customer knows by heart and uses to judge the whole store; it exists to bring people in and almost always has a low index. The second is what holds up the average. A healthy mix is not one with only high-margin items — it is one that uses the traffic items to fill the store and makes sure the basket they go into carries the others.
That is why the decision to take an item out of the catalog is rarely settled by looking at the item. Low-volume products that pull an entire basket — the specific brand that makes the month's shopping happen there — are worth the space they take up even with a modest individual contribution. What decides it is the basket they appear in, and that is only visible on the receipt, not on the product sheet.
The classic ABC curve ranks items by revenue and solves purchasing and inventory. For price, the useful ranking is by total contribution: the item with the most revenue is often the one with the thinnest index, and what holds up the month tends to be in the lower half of the revenue list. Swapping one ranking for the other changes who gets the endcap display — and it is the cheapest change there is in a store's result.
Where reading the mix tends to go wrong
The four below lead to the same wrong decision: giving space to what brings in revenue and taking space from what pays the bills.
Ranking the mix by revenue
The item with the highest revenue is, almost always, the one with the most compared price and the thinnest index. Ranking by revenue puts at the top of the list exactly whoever contributes least per real sold, and that is the list that tends to guide display and promotion. The ranking that serves for deciding price is each item's total contribution in the period.
Confusing the catalog mix with the sold mix
A store can have half its catalog in wide-margin categories and sell eighty percent in two thin-margin lines. The assortment describes the intention; the share describes what happened. Planning price from the first and determining results from the second is the mismatch that keeps the projected margin from ever matching the realized one.
Always promoting the same line
Promotion shifts share, and a line promoted every month starts to account for a larger slice of revenue with its index squeezed by the discount. Revenue grows, the average contribution falls and the break-even point rises. The effect is slow and shows up as "sales grew and the result did not" — which is the exact sentence of a mix that has been changing by itself.
Cutting the long tail by looking only at the item
Low-turnover items are the first to show up in a catalog cleanup, and some of them are the reason the whole basket happens at that store. Before cutting, it is worth looking at which receipts the item appears on and what else goes with it: the cost of losing the basket is often greater than the shelf space freed up.
The terms that decide price together with this one
No pricing term explains itself alone. These are the ones that appear in the same decision, each with its definition and its calculation.
Further reading
What the blog has already published about product mix and about what this definition addresses.
Understanding the calculation is one thing; redoing it across thousands of items is another
For one product, any of these calculations fits in a spreadsheet. Across an entire catalog, with cost changing on every incoming invoice, it stops being done — and the price ends up inherited from the previous month.