Retention

The share of customers still active after a given period. The inverse of churn, and usually the more useful way round.

Example

Of 100 people who signed up in January, 42 are still using it in April — 42% three-month retention.

Retention is the closest thing to a truth serum a startup has. Acquisition can be bought; retention cannot.

Churn — The rate at which customers or revenue leave over a period.
Cohort analysis — Grouping users by when they joined and following each group over time.
Product-market fit (PMF) — The point at which you have built something a specific group of people genuinely want, evidenced by their behaviour rather than their compliments.

Knowing when to change direction — Persistence and stubbornness look identical from the inside. Deciding in advance what would change your mind is the only reliable defence. (12 min)
Funnels and conversion — Find the biggest leak, not the easiest one. Most founders optimise the top of the funnel while losing 90% at activation. (12 min)
Retention, referral and growth loops — A funnel needs constant refilling. A loop reinvests its own output. The difference decides whether growth compounds. (12 min)
What to measure, and what to ignore — Different stages need different numbers. Measuring everything is the same as measuring nothing. (12 min)
Activation and retention — The two numbers that predict whether a company works. Acquisition can be bought; these cannot. (12 min)
Cohort analysis — Group users by when they joined and follow each group. It is the only way to tell real improvement from a growing pile of signups. (12 min)