What is an Impact Mapping?
Impact mapping draws a four-level tree from goal to backlog: Why (the measurable goal) → Who (actors who can move it) → How (behavior changes we want from them) → What (deliverables that might cause those changes). Every feature must trace to a behavior change that serves the goal — or it doesn't get built.
Its power is the deliverables it kills: most backlogs shrink dramatically when each item has to justify its causal chain.
Worked example
Goal: cut support tickets 30%. Who: new customers (60% of tickets). How: complete setup without calling. What: guided onboarding, config validation, better error messages. The team's beloved chatbot project appears nowhere on the map — no behavior chain reaches the goal — and dies in the workshop, freeing a quarter's capacity for the three items that do.