Fred ReichheldThe One Number You Need to Grow, HBR 2003
Ask how likely customers are to recommend you (0–10); promoters (9–10) minus detractors (0–6) yields a single loyalty score linked to growth.
Reichheld, Darnell & BurnsWinning on Purpose, 2021
NPS matures into a system: earned growth — measurable revenue from returning customers and referrals — is the accounting-grade companion to the survey score.
The EclipseFrontiers® LensNPS is a thermometer. Treatment happens in the follow-up.