The NPS and the ACSI: A Critique and An Alternative metric

The Net Promoter Score (NPS) and the American Customer Satisfaction Index (ACSI) are metrics used to predict sales, profit and share price change. We identify problems with the design of both the NPS and the ACSI. In particular, we find that the NPS does not measure negative word of mouth effectively, and we argue that the ACSI is similarly insensitive to dissatisfaction. This is because ex-customers and never-customers are not sampled in these metrics, and these are the people who express most of the negative sentiments about brands/companies. We propose a method of measuring the effect of word of mouth using the volume and mean impact on purchase probability of both the positive and the negative word of mouth expressed by users of the category.