NPS is a Cockroach. But There's Something More Important.

By Aarron Spinley [Original article for LinkedIn, June 26, 2025]

You know, it's a funny thing. NPS, belatedly, is part of the curriculum in my class. But it sure didn't start that way, not that I was trying to diss it. It's just that once you understand valid customer management methods, it's simply not a system-relevant test, and so there was no reason to teach it. Oh, and it doesn't work, which I'll come to. 

Eventually, though, I was forced to include it, simply because it came up so frequently in testing and Q&A. The section in the lecture is entitled "the elephant in the room". That's how omnipotent it's become, even after it was pronounced dead, had its final rites read, and all its relatives got fall-down drunk at the wake.

A genuine cockroach.

Not because of its own staying power, mind you, or some mythical capacity to survive Armageddon or a zombie apocalypse or an asteroid strike. But because way too many people who claim expertise in the customer field, which is desperately hard to detect, seem determined to breathe life into the little monster.

And so, yes, I am occasionally guilty of prodding a few souls on LinkedIn who, while always well-intended, either promote the cockroach years after its demise, or intellectualise about some pseudo-debate as to its worth. I've done so at conferences where I've been speaking, too, and during Q&As. 

Invariably, of course, some come for me, staring me down and daring me to substantiate my heresy. Others, a fair few to be fair, demonstrate an authentic pursuit of knowledge on the subject and ask me to explain further. I'm fine with both, to be honest, though I do respect the latter a smidge more.

So then. This is in service to both, and in my own service too if I'm honest. From now on, I'll send them this link. If you're here because of such an exchange, you're very welcome.

The Insecticide

There have been many empirical studies that, despite attempts, failed to replicate Bain's core claims about NPS. The critiques were many, beginning with methodological issues with the original NPS study. For example, it assessed past but not future sales growth rates by simple correlations with static NPS levels, measured at only one point in time. 

Not kosher.

But over time, these methodological concerns gave way to even more substantive ones. The cumulative findings across studies established that favourable NPS does not enjoy a causative correlation to growth (market penetration), is not a predictor of sales, and more broadly, is not a measure of loyalty. These are Bain's core claims. Oh dear.

In addition to these already terminal findings, the volatility of the scoring method, where marginal changes in the distribution can cause material changes to the 'net' score, render it wholly unreliable as to trend, and prone to non-representative fluctuations. And that's all before you factor in the gross unreliability of self-reporting in the first place. 

If you're an executive with NPS tagged to your performance reviews and income, don't ignore that bead of sweat forming on your brow. Turns out, it's not remotely the "only number you need to know" and is, in fact, a number that you should do your best to forget you ever heard of.

Now, it's about this point where I remind you that I am but a humble teacher. I don't have a dog in the fight. If the data had found the opposite, then that's what I would teach. It doesn't. But for those still staring me down, you don't have to take my word for it. Feel free to feed at the trough.

• “The Value of Different Customer Experience Satisfaction and Loyalty Metrics in Predicting Business Performance,” by Morgan and Rego‍
• “A Longitudinal Examination of Net Promoter and Firm Revenue Growth” by Keiningham et al.‍
• “Net Promoter and Revenue Growth: An Examination across Three Industries” by John Dawes.‍
• “The Use of Net Promoter Score to Predict Sales Growth: Insights from an Empirical Investigation” by Baehre et al.

Of course, it's hard to go too far in the world of marketing science without bumping into Byron Sharp, figuratively at least, or the work of his colleagues at the Ehrenberg Bass Institute. And even though one of those, John Dawes, is already cited above, it would seem remiss not to reference some of Sharp's contributions. Here are two.

• "Net Promoter Score Fails the Test"‍
• ‍"Net Promoter Score (NPS) Does Not Predict Growth – it’s fake science"

Enjoy. You'll need a cuppa.

The Anatomy of a Cockroach

Before you dive in, though, it's worth stepping back from this little rabbit hole. Because, despite the importance of understanding what works and what doesn't, it is in that same vein that we should discern the wider pitfall. 

The facts of the matter are that, despite appearances, shareholders of the very influential feedback industry don't particularly care about NPS or CSAT, for that matter, or any other acronym. And there are many. No. For them, the flavour is far less important than ensuring enough card-carrying CXers believe in such measures, valid or otherwise, just enough to dispatch as many surveys as possible into the ether. This is what their business model relies upon. 

It's a much bigger game than NPS alone.

Case in point: The current handwringing and hyperbole over artificial intelligence provides another smokescreen, where the faithful brethren are led through a different door, albeit to the same destination. This time, the sign reads "AI-activated insight" or some other jargon. In the same way that it has long applied statistical analysis to obfuscate the junk status of most feedback data, it now does so with the current drug of choice. AI. 

But the underlying data is still..." Leans back. Taps his pipe. Shifts his weight forward and looks you in the eye ... bollocks. 

Excuse the scientific language.

Of course, there are exceptions, meaning that there are valid uses of surveys and the capture of feedback, but you'll need to know the difference.

In the meantime, though, a foundational understanding of human consciousness and the workings of memory makes it plain that much of the feedback proposition is nonsense. For other reasons entirely, this exact knowledge is important in the fields of marketing and customer management, and those already in possession of it are somewhat shielded from the overreach of the feedback industry and other misuses of technology, as a result.

Education, AKA knowledge over belief systems, tends to do that.

The other key piece to this puzzle is this. Measurement is an extension of the system itself. This is systems theory 101. What that means is that to understand how to measure something, you must first understand the model of the system required to manage the asset, and even before that, the definitive attributes of the asset itself. So it's asset, to system, to measurement. 

But one of the endemic problems in the CX community is that it doesn't understand the first two. There is little surprise, then, that effective measurement eludes it, and that perceived shortcuts such as NPS appear so attractive.

Closing the Wonky Loop

Given the sheer weight of evidence, it's not surprising that the high priest of the NPS religion, Fred Reichheld himself, is also watering down its perceived importance, although he blames the collapse of survey response rates and a claimed misuse of the tool, not the tool itself. Naturally.

No doubt, Bain has long known that the body of independent data has dethroned its beloved child, but now that they are busy trying to hawk their next measurement trip, which seems an increasingly popular shell game of various consultants, even their reliance on NPS is perhaps nearing its end. 

It matters little. 

We are already in possession of highly effective means of both governing and measuring the customer asset. The rituals of service date back five thousand years, give or take a long hot summer, offering a depth of historical and compelling economic precedent. Equally, the important repeating patterns of market-based economies, and of the corporate customer base itself, are empirically established, as are the relevant operational disciplines that they inform. 

Armed with all of that, and its application in the current era, you'll stride confidently into any boardroom in the world, able to brief them on the workings of their customer base, and all without a single piece of feedback. How's that for a loop?

Oh, and you certainly won't need NPS. You never did.