A few definitions are offered. Here's an exercise in gobbledygook from an agency: "any stimuli or any marriage of a brand with a shopper or consumer along the shopper continuum which turns them from consumer to shopper to buyer." Which is so broad as to be meaningless.
Something more to the point is this from Kimberley-Clark:
K-C officially defines shopper marketing as "integrated-marketing programs based on a deep understanding of shopper attitudes and behaviors designed to build equity for the brand and differentiate the retailer while the consumer is in shopper mode and prepared to make a purchase," said Mark Scott, VP-sales and shopper marketing.It's often said that "you can't manage what you can't measure." It's equally true that you can't measure what you can't define. I've written before that I see Shopper Marketing as being the nexus of trade promo and brand advertising which, if correct, would mean that such promotions would need to be measured in ways similar to traditional media (e.g., reach and frequency), and also in trade promo terms (volume lift, incremental profit, etc).
The aborted PRISM initiative was an effort to develop the former, while several companies offer the means to do trade promo measures. But there still is no consensus definition, which means that there are no consensus measures, which means that establishing best practices and benchmarks is still somewhere off in the future.