In 2003, The Harvard Business Review published an article by a consultant named Fred Reichheld, called The One Number You Need to Grow. In this article, Fred described how asking a single question, on a numeric scale, could predict customer loyalty and, subsequently, business success. He called his measure the Net Promoter Score (NPS).

Though lots of businesses still use it, it turns out that the Net Promoter Score doesn’t predict either loyalty or business success. By itself, the score proves to not be any more useful than following the horoscope in the daily newspaper.

Other measures have tried desperately to fill the void left by NPS. The System Usability Score (SUS), Customer Satisfaction (CSAT), and others all try to deliver a single number to tell us how we’re doing. None of them are any better than NPS.

No single metric will tell us how we’re doing.

The theory of a grand unified metric goes like this: By benchmarking competing companies on this single metric, we can get a relative idea of who is delivering the best experience for customers. Organizations pay consultants big bucks to get their products and services measured. The consultants deliver reports around a unified measurement, which companies review with a fine-tooth comb. They seek any indication on how they could boost their score, hoping to someday be in the lead.

Boosting a consultant-provided score seems like a great goal, until you realize it has no relationship to the experience the organization delivers to its customers and users. Improving the score becomes a game. A game not related to the important things that make the organization competitive in the market. Unlocking the secret to improving the score will not unlock a better user experience.

Unfortunately, the theory that a grand unified metric can tell us how well our products and services are doing is just a myth. No such metric actually exists.

There are many ways to measure success.

Imagine a bakery. It could sell the tastiest cupcakes and pastries. Or it could be the cheapest bakery in town. Or it could have the best atmosphere for a relaxing meetup with a friend or two.

It’s unlikely it would be all three. Why should it? There’s plenty of business for bakeries of all types.

The bakery owner striving to have the best atmosphere shouldn’t use the same measurement of success as a baker trying to offer the cheapest baked goods. The metric the bakery owner should use needs to be specific to the goals of the business, not generic across all businesses.

Every product and service experience needs unique metrics.

Organizations should strive to be different from their competitors. They work hard to offer the best value for their customers.

But that value is unique to that organization. It’s ironic when organizations — working hard to create their unique value proposition — want to have a common measure to rank themselves against their competition.

If their proposition is indeed unique, then so is their competitors’. Everyone is striving to end up in a different place. Using a single metric to determine who is the best would require every value proposition be identical, not different.

We need metrics that are unique to our own value proposition. We need to remember why our product or service makes the world a better place. Then, using that as a basis, we create UX Success Metrics.

Measuring our success will require that we strengthen our UX research game. We’ll need more sophisticated techniques for connecting the improvements we make in our designs to improvement in the business. We’ll do this by translating our findings into the language that our executives speak.

We can measure our improvement, but we need to do it on our terms. We shouldn’t try to divine what these consultant-driven metrics packages pretend to tell us. We should drive our organizations by what it really means to deliver well-designed products and services.