Bundles and basket size: what the research says about letting shoppers choose

Every order carries its own picking, packing and shipping cost. A bigger basket spreads that cost over more items. The research below asks whether bundles help build that basket. None of these studies measured a Shopify app, and none gives a reliable size for a bundle uplift in order value. They give the money logic and one warning.

Why a bigger order matters

McKinsey: “Fulfillment costs, for example, can account for 12 to 20 percent of e-commerce revenues, squeezing margins and making profitability a mirage.” It adds that “higher item value and basket size in categories such as home, sporting goods, and electronics incur lower shipping costs as a percentage of sales.” This is e-commerce in general. It does not say how much a bundle raises order value.

Shoppers who choose bundles buy more

Kobuszewki Volles, Ribbers, Van Kerckhove and Geuens, in the Journal of Retailing and Consumer Services, ran “three experiments, supplemented with two studies and a meta-analysis.” They report that “incorporating bundles into the assortment and having consumers select these bundles increases overall purchases.”

Their explanation is about perception: shoppers see the bundled items “as a unified whole,” which alters how they see the products fitting together and “leads them to underestimate their total purchases, prompting them to buy more.” The setting was grocery meal bundles, and we read the abstract only, so there is no effect size to quote and no proof it carries over to your products.

Shoppers judge a bundle on its one price

McKinsey describes a high-end accessories retailer that tested bundles. “When the retailer bundled two items typically bought together for an out-the-door price of $499, customers paid attention only to the price of the bundle; they didn’t even notice price changes on the individual items.” Its gain of more than 50 percent in EBITDA (earnings before interest, taxes, depreciation, and amortization) in the test categories came from its whole pricing strategy, not from bundles alone.

The warning: rigid bundles mostly move shoppers between brands

Foubert and Gijsbrechts, in the Journal of Marketing Research, studied bundle promotions for packaged goods. They found “promotional bundles are far more effective at inducing switching than at boosting category sales,” because “the purchase quantity requirement is often too stringent to make consumers buy earlier and/or more in the category.” A fixed bundle that forces one combination may mostly shift choice rather than grow the basket. We found no study that measured whether a bundle the shopper builds changes that. That is a gap, not a result.

What to do this week

• Count how many of your orders carry a single item, and which items are bought together.
• Build bundles around items already bought together, and let shoppers pick the size or colour of each item.
• Keep stock on the real items, not on a separate bundle product.
• Check the margin before you discount: the extra items have to pay for the bundle discount.