Finding product-market fit (PMF) is the Holy Grail for startup founders. Figuring out if sustainable demand for your product exists is something you want to do as early as possible so you can change course or make the necessary adjustments. However, many startups only realize they don’t have PMF well after going to market. This article will look at how you can identify and achieve PMF, even if things aren’t quite going as expected. Image by creativeart on Freepik What is the 40% Rule? Sean Ellis is well-known in the software development space. In a legendary 2010 blog post, he coined the term “growth hacking ,” which revolutionized how founders think about product marketing. As if that were not enough, he also popularised the Sean Ellis Rule, also known as the 40% Rule. The 40% Rule is very straightforward. All it requires is asking your users one simple question: "How would you feel if you could no longer use our product?" The respondents then have a choice of one of...