Our research into the link between Net Promoter and growth was conducted in two parts. For the first investigation, we examined data from a two-year study of more than 8,000 customers of companies in three industries (retail banking, mass merchant retail and Internet services) to explore the relationship between customers' survey responses and their subsequent loyalty behaviors. Individual customer ratings on common satisfaction and loyalty metrics were monitored over two years. In the second year of the study, customers' purchasing (retention and share of wallet) and recommendation behaviors were also tracked.
For the second investigation, we conducted two experiments. In the first we used a comparable data set representing more than 15,000 consumers and 21 companies from five industries from the Norwegian Customer Satisfaction Barometer to calculate each company's Net Promoter Score using Frederick Reichheld's own methodology. We calculated and compared the results with several other leading customer satisfaction and loyalty metrics, and analyzed the links to actual revenue growth performance.
In the second experiment, we replicated a subset of Reichheld's data for three U.S. industries he cites as exemplars of Net Promoter in his book The Ultimate Question (airlines, personal computers and life insurance). We replicated the scatter plot diagrams for these three industries to directly compare the relative performance of Net Promoter with that of the American Customer Satisfaction Index, a national economic indicator of customer evaluations of the quality of products and services available to household consumers in the United States. We then compared Reichheld's re-created data with that from the ACSI for the same time period.