The myth: A good program increases how much members spend in the category overall, not just with you.
By Tim Tyler, 6th October 2026
This is the most technically grounded myth in the list, because the evidence against it is specific and replicable.
The NBD-Dirichlet model — developed by Andrew Ehrenberg and colleagues across decades of research in packaged goods and retail — describes how buyers behave in stable categories. One of its central findings is that purchase frequency across a category is remarkably stable for a given consumer. People who buy coffee four times a month buy it four times a month. Customers who buy fast food twice a week buy it twice a week. A loyalty program can shift where those purchases go (increasing your Share of Category Requirements), but it's very unlikely to increase the total number of coffee or hamburger purchases.
There are exceptions: categories where consumption is genuinely elastic (restaurants, entertainment, discretionary retail) may see some spend stimulation from a compelling program mechanic. And programs that introduce customers to adjacent categories within the same brand portfolio can shift total basket value. But in most stable FMCG and grocery categories, the Dirichlet prediction holds: the program moves share, not volume.
This matters for how you set program objectives. If the business case depends on members spending more in the category overall, it will almost certainly disappoint. If the business case depends on members spending a larger share of their existing category budget with you, it's testable and potentially achievable.
SCR improvement is a legitimate program goal. Category expansion usually isn't.
The program competes for a share of what members are already spending. It rarely changes the total amount they spend.
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