Fred Reicheld, ideator of the Net Promoter Score (NPS) score, acknowledged that different scoring scales could be used and even provided a case study using a 5-point scale.
Additionally, our expert research suggests that whether we use a 5-point or 11-point question scale, we measure the same underlying feeling/intention.
Why the 0-10 NPS scale isn't necessarily the best scale
The NPS customer-focused response scale ranges from 0 to 10 (11-point scale). These types of score 'out of 10' methods were once common for telephone interviews. Additionally, researchers start the scale at 0 because sometimes people would mistakenly use 1 as a good score. But, scales from 0-11 are much less user-friendly for digital surveys, even more so on mobile devices. The majority of evidence suggests that fully labeled response scales are the most reliable response method.
The 0-10 eNPS scale or any other single question is never as reliable an outcome measure as a multi-question index
It's common statistical knowledge and recommendation that when it comes to self-report scale metrics for a critical outcome, we are far better off using a multi-question approach (e.g., we combine 3-4 questions into a single index for Employee Engagement). Customer and market research studies have shown that using multiple questions is more reliable and accurate than using a singular NPS-type question or metric.