Cohort Retention Curve
A cohort retention curve plots what percentage of a group of customers who joined in the same period are still paying, month by month, after they signed up. You group customers by when they started, then track how that group shrinks over time. The shape of the curve is what matters: a curve that drops fast then flattens means you lose some early but keep a loyal core; one that keeps sliding means churn never stops.
For a founder this is the clearest picture of whether your product has real staying power. A flattening curve is the signal of product-market fit, because it shows a stable base that does not leak away. Comparing curves across cohorts tells you whether changes you made, to onboarding, pricing or the product, are actually improving retention for newer customers. It is far more honest than a single churn number, because it shows you when customers leave and whether the situation is getting better or worse over time.