Net Promoter Score (NPS).

The Net Promoter Score comes from Bain & Company's Net Promoter System and was introduced by Fred Reichheld in the Harvard Business Review in 2003 (article 'The One Number You Need to Grow'). The question is: 'How likely is it that you would recommend us to a friend or colleague?' Answers are given on a scale from 0 to 10. A 9 or 10 counts as a promoter, 7 and 8 as passive, 0 to 6 as a detractor. NPS is the percentage of promoters minus the percentage of detractors (source: Bain & Company, netpromotersystem.com).

The strength of NPS is its simplicity. One question can be asked after every job, once a year or after a support case; response rates are higher than for long surveys, and the score is comparable over time. The open follow-up question is crucial: 'What is the main reason for your score?' Only these answers show what needs improving. The number on its own is a thermometer, not a prescription.

NPS has well-known limits. With small numbers of customers it fluctuates heavily: a few answers more or less move it by many points. Cultural differences play a part too: people who rarely give top marks end up as passives even when they are satisfied. And the score measures an intention, not whether recommendations actually happen. Comparisons with other companies are therefore risky. The trend within your own business, broken down by customer group, is more telling.

NPS complements other signals rather than replacing them. Public Google reviews are visible to new customers and part of online reputation management, whereas NPS is an internal measure. Detractors are an early warning sign of churn, see churn rate. Promoters are the natural people to ask for a review, a reference or a referral, which together build social proof.