The Net Promoter Score (NPS) is widely used as a way of assessing client loyalty, but its suitability for professional service firms is often debated. While it is recognised for its simplicity and senior‑level appeal, its effectiveness depends on how results are interpreted and whether it is used in isolation or alongside other measures.

What is NPS?

The Net Promoter Score (NPS) is a metric designed to gauge how loyal a firm’s clients are. It was developed by Bain & Co as a way of linking client advocacy to business growth through a single, standardised measure.  It is based on responses to one question: How likely would you be to recommend our service or firm to a colleague?

Clients respond on a scale from 0 to 10, with answers grouped as follows:

• Promoters (9–10) are loyal supporters who are likely to recommend the firm
• Passives (7–8) are satisfied but unenthusiastic clients who may be open to alternatives
• Detractors (0–6) are unhappy clients who may damage reputation through negative word of mouth

The score is calculated as:  % Promoters – % Detractors = NPS

NPS became widely adopted as web‑based surveys increased in use, particularly in consumer‑focused sectors where large sample sizes and regular measurement made a single‑question approach practical. Its creators suggest that it captures customer experience and can be used to predict business growth.

What is a good NPS score?

NPS is an index rather than a percentage, with scores ranging from –100 to 100. Benchmark data is available across many industries, although meaningful comparisons rely heavily on consistent sampling and methodology. In broad terms, a score above zero indicates more promoters than detractors. Scores above 50 are often described as excellent, while scores above 70 are sometimes referred to as world‑class. Professional service firms frequently report high NPS scores, but these should be interpreted with caution, as the nature of professional relationships differs significantly from transactional consumer models.

The pros and cons of NPS

NPS has generated extensive debate, with research and practitioner opinion both supporting and criticising its use.

Advantages of NPS: 

• NPS works well as a simple, high‑level data point that senior teams can easily understand and discuss. It has strong recognition and credibility, which means it is often trusted at board level. The approach is straightforward to implement, measure and calculate, with no complex statistical requirements.

• NPS can also be used as a benchmarking indicator, provided the way feedback is collected and the client sample included are genuinely comparable.

Limitations of NPS

• NPS lacks diagnostic depth and does not explain the reasons behind a score or the context of a client’s experience. It does not account for the relative importance or influence of individual clients, meaning a critical relationship carries the same weight as a marginal one.
• Cultural differences can affect how respondents use rating scales, with some clients avoiding extreme scores altogether. In professional services, sample sizes are often small, making results more volatile and less reliable.
• The measure is also vulnerable to gaming and is poorly suited as a performance target for frontline teams. When scores are compared between firms, or against published benchmarks, it is often unclear whether datasets are genuinely comparable, particularly in terms of client type, relationship depth or selection bias.
• Sample composition, response bias and question framing can all materially influence the final score.

Alternatives for measuring client loyalty

Client relationships in professional services are complex, long‑term and highly nuanced. As a result, relying on a single metric rarely provides a complete or reliable picture of loyalty.  Experience suggests that a combination of measures is more effective, allowing firms to understand not only advocacy, but also relationship strength, risk, dependency and future intent. A broader approach helps firms move beyond headline scores and focus on meaningful insight and action that supports long‑term client relationships.

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