Breaking into a bank vault and taking only a bag of pennies is like doing Voice of the Customer research without 40 interviews

Matt is struggling to improve his product development group’s productivity. Why, he wonders, do Voice of the Customer (VoC) experts make at least forty customer interviews? 1,2,4

Why 40 interviews?

Matt reached out to Andy for advice on how to add VoC into Matt’s existing development process. Andy is an advisor to Matt in his quest to cut in half his group’s cumulative cost to develop a successful product. Fifteen years ago Andy added VoC to his company’s process. Although he has made other process changes, VoC remains his method to reduce market risk.

Andy stressed collecting at least 40 in-depth interviews in the idea’s ecosystem. Otherwise Matt’s group will only understand a fraction of the idea’s value to customers. They will not see emerging patterns of why customers need key product characteristics. They will miss the opportunity to unearth a latent need, triggered by a description of the idea.

Andy said it is common for developers new to VoC to stop after a few interviews.   But, they are not used to the richness of information elicited by a VoC interview. So they feel they’ve finished measuring commercial potential and reducing market risk. But, said Andy “they are wrong.” “They got into the bank vault, picked up only a bag of pennies and ran.”

Budget and time limitations

Some companies handle front-end, development risk in an ironic manner according to Andy. Their risk reduction budget targets reduction of technical risk. Meanwhile reduction of market risk, the major front-end risk, is starved for money and time.

His advice was to add VoC to the front end of Matt’s current product development process. Yes, the current cost to shape a idea for a development decision would increase. But, lowering the market risk in the front end cuts the cumulative cost for a successful product in half.2 Matt’s group will stay within the current budget and time limitations. But they will produce twice the number of successful products.1

In the late 1980s, I heard Professor Griffin describe her pioneering work on VoC.4 Since then, I’ve used VoC to uncover customers’ requirements for client’s product ideas. Like Sherlock Homes, I elicit undiscovered data, information. and insights from strangers. Holmes did most of his elicitation work face-to-face rather than on the phone. I only use the phone.

Among the benefits of phone elicitation are:

– Quick to reach knowledgeable people for elicitation conversation

– Great openness of the conversation

– Much lower cost


  1. (2017) Castellion, G. How To Develop A Successful Product For 48% Less
  2. (2013) Markham, S. K. The Impact of Front-End Innovation Activities on Product Performance J. Prod. Innov. Manag. 30 p77-92

Markham defines front-end activities as work done to develop a product concept before the NPD project enters the commercialization phase of a formal product development system. Such work includes simple demonstration of technical feasibility, a sensible understanding through VoC of how, why and when a concept’s acceptance the marketplace will occur, and a back-of-the-envelope financial viability analysis.

  1. In a confusing “borrowing”, some companies describe traditional customer satisfaction research as VoC. I once asked the VP of VoC at such a company how many times per month the VP talked to customers. The reply: “Oh no, I never talk with customers. I represent the voice of the customer at meetings where I interpret Net Promoter Score (NPS) findings on our company.” (NPS measures the loyalty that exists between a provider and a consumer.)
  2. (1993) Griffin, A. and Hauser, J. Voice of the Customer Marketing Science 12 p1-27