Net Promoter Score (NPS) is a KPI used to assess overall customer satisfaction and how likely customers are to recommend a company to a peer or colleague. The score is derived from the response to a single question: “How likely is it that you would recommend our offering (product, service or company) to a friend or colleague?” This is scored on a scale of 0 (not at all likely) to 10 (extremely likely). The metric is typically calculated as the percent of promoters (those scoring 9 or 10) minus the percent of detractors (those scoring 0 through 6). Net Promoter Score and NPS are registered trademarks of Bain & Co., Fred Reichheld and Satmetrix Systems.

Social Proof: Why We Look to Others For What We Should Think and Do
When we feel uncertain, we all tend to look to others for answers as to how we should behave, what we should think and what we should do.