If you’ve spent any time around Zingerman’s over the last decade, you’ve probably heard us talk about ZXI. Maybe you’ve filled out a survey after a visit and been asked one simple question: on a scale of 0 to 10, how likely are you to recommend us to a friend?

That question isn’t ours. It comes from Fred Reichheld — the Bain Fellow who created the Net Promoter Score (NPS), the customer loyalty metric now used by companies worldwide. We adapted it years ago as the Zingerman’s Experience Indicator, our own homegrown version of the same idea: customers respond to that single question, and we use their answers to track how well we’re delivering great experiences. A 9 or 10 makes someone a promoter, 7s and 8s are neutral, and anything 6 or below flags a detractor.

Why one question changed how we work

It sounds almost too simple to matter. But tracking ZXI has taught us something we didn’t expect — our resources are best spent on customers who are already fans, turning promoters into lifelong regulars, rather than pouring all our energy into winning over the lukewarm or unhappy. That’s a real shift in mindset, and it’s one a lot of businesses never make because they’re measuring the wrong things, or nothing at all. (Read more on how ZXI reshaped where we put our energy: “Loyal for Life”)

Ari first came across NPS at a conference, hearing Intuit’s Scott Cook describe how the metric shaped the company’s strategy. That sent him looking for more, and he landed on Reichheld’s book as the clearest explanation of how and why it works. What followed was years of putting the idea into practice inside a company that already prided itself on service, and learning just how much a single well-designed number can sharpen that instinct into something measurable and repeatable. (Ari tells the full story here: “ZXI: A New Way to Measure Service”)

Why referrals, specifically

Fred’s newest research goes a step further than the score itself. In his book Winning on Purpose, written with Darci Darnell and Maureen Burns, he introduces a companion metric called Earned Growth Rate — a way of tracing how much of a company’s growth actually comes from customer loyalty, rather than just spending on new-customer acquisition. It has two parts: net revenue retention (how much revenue you keep from existing customers) and earned new customers (revenue from people who showed up because someone else told them to). (Forrester breaks down how the metric works)

The finding that keeps showing up in his research: referred customers are usually a small slice of new business — often around 20% — but they drive a wildly disproportionate share of profitable growth, sometimes 70% or more. Fred calls that referred segment a company’s “magnetic core.” Most businesses have no idea this dynamic exists in their own numbers, because almost nobody is set up to measure where a new customer actually came from, let alone what they’re worth. (more on the “magnetic core” concept)

That’s the conversation we’re bringing to Ann Arbor: Fred sitting down with Ari to talk about what separates a true promoter from a merely satisfied customer, why referrals get overlooked even by companies obsessed with customer experience, and what it actually takes to build a culture where advocacy shows up on its own — not because you asked for it.

Join us

The Power of Referrals A conversation between Zingerman’s Ari Weinzweig and best-selling author Fred Reichheld, creator of the Net Promoter Score

📅 Wednesday, October 7th, 9–11am 📍 ZingTrain 🎟️ $95/ticket — includes breakfast and a copy of Fred’s new HBR article