If your customers don't talk, NPS is a vanity metric

Clearly the less fuzzy way to define it is "How many people have you recommended this product/service to in the last n months?" not "Would you, if asked?"

Also, whether customers talk to each other (directly, privately) is not the only thing, there are online reviews, resources like HN, etc. And it's always hard to tell what's compensated or not, e.g. Snowflake's "grassroots" testimonial campaign on LinkedIn, testimonials etc., with the huge budget.

The other thing the article misses IMO is that detraction is also growth, albeit negative growth (and additionally, people are in my experience much more likely to passionately recommend _against_ something they hate than recommending something they love). So the NPS tells you a thing or two about: - Your potential to utilise whichever chance you have to grow via word of mouth - Your potential to squander that same chance due to people hating your product - Your potential to have negative growth because your customers are leaving in droves.

> They can't; there are people who answer 10 but will never recommend, and there are people who answer 0 but already have and will again.

What matters with NPS is trend over time, and getting the numbers at a scale. Yes, there are people who randomly click on one end of the scale or the other, but the assumption is that on average the portion of these people is stable.

> Next, you assume your customers are idiots and don't know how an 11-point scale works by adjusting the midpoint: Instead of 5, the middle is now 7 and 8.

This does not come from the assumption customers are idiots, it comes from the idea to treat people who vote "in the middle" not as neutral, but as detractors. Which makes sense: If someone tells me "hey I know Product X and it's meh", then I'm less a promoter but more a detractor.

> Then you realize there are two many numbers, so you throw several out by reducing your 11-point scale to a 3-point scale

The 3 point scale was the goal all along though, it's the idea of an asymmetric scale that leads to the 11-scale to 13-scale reduction.

> after which you re-interpret "unlikely to recommend" as "likely to snag some other customers on my way out the door."

If your assumption is that promoters drive positive growth, it's fair to assume that detractors drive negative growth by recommending an alternative. If you believe in that core assumption that NPS measures word of mouth, then this interpretation of "likely to snag some other customers on my way out the door" is a sensible one.

> NPS is said to measure growth using loyalty as a proxy. But then, what does that have to do with recommendations? Nothing. I don't think the underlying assumption is bad. That's how influencers work: people are more likely to buy something that is being recommended to them by someone they trust and someone who is passionate about the product.

Does NPS work? I don't know - I'm not using it as I said above. But at least the assumptions under which NPS are designed on top of the idea of word-of-mouth as a growth diver seem solid to me.