The Effect of The Net Promoter Score on Sales: A Study of a Retail Firm Using Customer and Store-Level Data

Existing industry-level evidence does not inform practitioners about when and by how much sales will grow as a result of an increase in NPS. We investigate the relationship between sales and NPS for a leading retail firm by combining individual stores’ monthly sales data with data from customer satisfaction surveys from which we calculate NPS for every UK store in every month over a four-year period. We find nonlinear sales effects of (i) stores’ own NPS and (ii) the average NPS of the other stores of the same company in the same region. Both NPS effects on stores’ sales at first increase and then decrease over the five to 10 months after the product purchases to which the NPS refers. If every store could achieve a sustained increase in its NPS of one percentage point, then across all UK stores the additional annual sales would be around £3 million.