Facebook VP of Growth Alex Schultz: “Retention is the single-most important thing for growth” Alex walks through how to calculate a retention curve for your startup (graph the percentage of monthly active users on the y-axis versus the number of days from acquisition on the x-axis). As he explains: “If you end up with a retention curve that asymptotes to a line parallel to the x-axis, you have a viable business, and you have product/market fit for some subset of market.” If you do not have a retention curve that flattens out, you do not have product/market fit and none of the growth hacking or virality tactics that people love to talk about will work. “Focus on getting to product market/fit… If you don’t have a great product, there’s not point executing well on growing it, because it won’t grow. The #1# problem I’ve seen inside Facebook for new products and the #1# problem I’ve seen for the startups I’ve advised has been that they don’t actually have product/market fit when they think they do.” Source: @ycombinator (Oct 2014)