"How would you feel if you couldn't use the product anymore?" According to growth hacking pioneer Sean Ellis, this is the question to ask to determine your level of product-market fit. In response, you are looking for at least 40% of your customer base who say they would be "very disappointed". This represents user passion.
Product-market fit is the degree to which a product satisfies a strong market demand. It is impossible to sustainably grow without product-market fit, ie. if people don't ultimately want what you've built.
If a company asks their users "How would you feel if you couldn't use the product anymore?" and 80% of users say that they would be "somewhat disappointed", that seems like a big number. Wow, 80%! But that doesn't matter. "Somewhat disappointed" isn't user passion. User passion is the best leading indicator of product-market fit.
Don't despair! Even if only some of your users would be "very disappointed", try segmenting them by persona. Perhaps among your users - college students, or finance managers, or female entrepreneurs, or whatever the persona - are the ones for whom your product is a must-have. According to Sean Ellis, figuring out who these people are and why the product is a must-have for them, and what is the difference between these must-have users compared to other users for whom it's just a nice-to-have, are at the root of scaling growth.
Those people who say "very disappointed" - talk to them! Ask them:
Of course, what people say can be different from what they actually do, so the other metric to follow closely is user retention. Although this is a lagging indicator rather than a leading indicator, users who stay for the long-term are signalling something about your product simply through their actions. It would be easy to simply assume those users stick around because of the product features, the vision, the messaging. But again, how are they actually using the product? Often it will be in unexpected ways, and isolating that is the gold you are after.
Full credit to Sean Ellis' The Increasing Overlap of Product and Growth.